She and Cosima stay in touch while Felicity is at M.I.T. It's nice to have someone to geek out with, even if their focuses are different. Cosima at least understands that excitement and drive.
Felicity graduates and moves to Starling City when she gets a job at Queen Consolidated. Cosima's excited for her, stating that she wants a tour of everything science related when she visits.
Felicity's never been more pleased that she trusted her instincts. Her friendship with Cosima has survived her four years at M.I.T. and Cosima finishing her bachelor's and working her Master's. And though she knows it probably won't be for a while, Felicity loves the fact that Cosima wants to visit.
…
When Cosima receives a call from a Detective Beth Childs, she doesn't know quite what to think. Genetic identicals is difficult to believe, but not impossible. It's probably because her focus is Evolutionary Development that she accepts Beth's story, especially when she's been presented with all the information. Which Beth apparently finds odd. It seems that she and the other clones Beth has talked to, were having a bit more trouble with the concept. What worries Cosima about the whole situation is who is out there hunting them all down.
She debates whether to tell Felicity, who is really her only friend. Not because she doesn't trust her, but because it doesn't sound real and Felicity would probably need proof. And does she really want to draw her friend in that deeply?
But she needs someone to talk to about it. And so she tells Felicity. What's interesting is that Felicity seems to have secrets of her own. They're both pretty bad at keeping secrets from each other—their relationship has always been very honest. And so during one late night chat, they both share.
...
When Felicity tells Cosima about how she spends her nights, she doesn't expect to be believed. But then Cosima counters with the fact that she's a clone and Felicity doesn't know how to respond. Cosima takes her silence as disbelief and so she holds up the photographic evidence as proof, making Felicity understand why Cosima was so insistent that this conversation be a video chat.
The fact that someone seems to be killing them off is scary as hell, making Felicity anxious about Cosima's safety—when she supposes it's only fair since her nightly actions aren't exactly safe.
So she does the only thing she can, offer to help. She may not understand the science of it, but she can definitely find things online, possibly even other clones.
…
Learning that Felicity, who is deathly afraid of heights, jumped out of a plane makes Cosima smile. It's a nice distraction from all the craziness that seems to be happening around her. Beth's suicide, Katja's murder and Sarah's appearance seem to have set things into even faster motion. Cosima had thought that just learning she was a clone was dramatic enough. Turns out she was very wrong.
As she tries to explain everything that's happened and what the knowledge of a new clone has brought, Cosima struggles with telling Felicity her true feelings about Sarah. Falling for a genetic identical feels... wrong, somehow—though she knows it's more about how others will perceive it. Or maybe she's just worried about Sarah's reaction. They obviously connect; more so than Cosima ever did with Beth or Alison. Sarah seems to understand that Cosima finds it all fascinating and while she might not appreciate it all the way Cosima does, she does accept it, just as she accepts so many things about their insane situation.
Felicity eventually drags it out of her, but doesn't judge her for it. She reminds Cosima that it's not like they're truly sisters—even if others might see them that way—that they didn't grow up together and isn't the whole point that they're all such different people?
Cosima feels a sense of relief. She didn't expect judgment, that's not really Felicity's style, but she'd still been nervous. Because even if nothing comes of it—because she really hasn't decided what she's going to do—the feelings will always be there. Felicity just tells her to call any time she needs to talk about it and leaves it at that.
…
Falling for Sara catches Felicity off guard. It's an unexpected delight amidst the worry and struggle as Oliver tries to forge a new way. She talks with Cosima about it, who is starting a new romance of her own.
Though she's glad that Cosima seems happy, Felicity does wonder if Cosima is pursuing her as a distraction from her feelings for Sarah. And finding out that Delphine might be Cosima's monitor is even more worrisome. Felicity just hopes things don't turn out too badly for Cosima.
Then again, she started dating her boss's ex girlfriend a mere week after they broke up, so maybe she has a reason to be wary as well. Watching them spar in the lair makes Felicity wonder if she's fooling herself. They obviously have great chemistry, plus the whole masked hero thing.
Diggle, out of all people is the one to reassure her—though he's always been the wise observer as long as she's known him, so she probably shouldn't be surprised. He sees things she may have missed and informs Felicity that Sara stares at her a lot more than she realizes. Except that Felicity's worry isn't about Oliver and what he might think, but instead wondering if she's the right person for Sara since she's so vastly different than Oliver or Nyssa.
"The only difference is that you haven't killed anyone," Diggle says.
"That seems like a big difference, Dig," Felicity retorts.
"Aren't you selling yourself short, Felicity?" he asks.
"No, I..." Felicity sighs. "I just really like her, Dig. I guess I'm worried that it's more one sided."
"Trust me, it's not."
And as the relationship grows, Felicity realizes he's right. Just because Oliver feels like he's not in the right place for a relationship doesn't mean that Sara feels the same way.
...
Cosima hadn't planned on telling Felicity that she's sick—especially since she's known for a while and had hoped she'd figure out a cure before things got too bad. She hadn't even really planned on telling Delphine, it had just felt right at the time. But when she has a coughing fit, complete with blood splattered in her hand, she really has no choice. She probably shouldn't have agreed to a video chat.
Felicity is concerned and offers to help with research, even if she doesn't really know what to look for. Cosima appreciates the offer, but she knows that Felicity has problems of her own. Felicity tells her she's being stupid that her computers are capable of running multiple searches and that she can even keep them hidden from the rest of the team. So Cosima, reluctantly explains about the spreading polyps.
…
Shit hits the fan and there's little time for chatting for either of them. They still keep in touch though, through texting mostly because they can't seem not to communicate. They've been friends long enough that they have a short hand so if someone else found the conversations, they'd probably wouldn't understand. Felicity sends quick messages about Slade Wilson and Starling burning while Cosima replies with snippets of how she gets out of DYAD's clutches and falling into a relationship with Sarah. Felicity worries because Cosima seems to be getting worse, but Cosima counters with her concern about Felicity being in the middle of a Slade's revenge and how she'll always be a target because she's on Team Arrow.
…
The fact that Delphine offers to step aside when she returns is something Cosima never expected. Delphine's always fought for the relationship, but in hind sight, Delphine's always done what she thought would protect Cosima. And apparently the closeness between her and Sarah is obvious. But what Cosima really didn't expect is that Sarah's willing to stand by her in any capacity that Cosima is comfortable.
For someone who has been alone a lot of her life, it's an amazing gift. Except she doesn't want to hurt either of them.
The decision is made on Felix's couch after a bottle of wine she probably shouldn't be drinking and many rambling debates between her and him. It seems obvious once it's realized, but she supposes she needed to get there on her own—well with a push from Felix.
At first Cosima worries that the easy acceptance from both of them is because they know it's what she wants and not because they think it's a good idea. But that worry disappears as her condition worsens.
They're so close to a cure, but she's doing downhill fast and she watches them bond in a way she never expected.
The cure is discovered just in time It's a long and difficult process, but it works.
...
Knowing that Cosima's found a cure is an obvious relief, though as Felicity listens to what it entails, she still fears for Cosima. It's not an easy procedure to go through and after all these months, it sounds even more draining than being sick. Still Cosima seems optimistic and is full of reassurances, so Felicity just hopes for the best.
…
As Cosima explains the cure to Felicity, she can tell her friend is worried. It's understandable since it's going to difficult. But she's made it this far, so Cosima knows she's going to survive.
And what's even more encouraging is the fact that the explanation sparks a memory for Felicity. She excitedly explains about something she read about months back that might help prevent the disease from attacking the others. She offers to research it.
…
Felicity's never been gladder to know people at STAR Labs. The fact that the cure has a different application and is something they already produce is almost as crazy as finding out that Cosima is a clone. She talks to Caitlin and after some negotiating and eccentric stories, Felicity is promised a dozen vials. She just hopes it's enough.
She contacts Cosima and eagerly invites her to Starling City to pick up them up, since it's easier for Cosima to fly out than it is for Felicity to come to her.
Cosima doesn't mind, stating that she'll just be bringing her entourage along and it'll be fine.
Felicity's excited; it's been a long time since she's actually seen Cosima in person. She's also curious to meet one of the others, especially Sarah—though Cosima never specified who was coming, Felicity knows that Sarah is the only one it could be since she refuses to let Cosima out of her sight for too long. An after effect of Cosima almost dying. Which means that Delphine will be coming as well, Felicity assumes.
So they plan a quick visit and tickets are brought.