She dumps Carol. She doesn't see she has any other choice because she can't live with the feelings of guilt which are invoked each time she thinks about Jack. When she tells Carol that she and Jack kissed he stares at her for a full two minutes before shaking his head and starts muttering about unresolved sexual tension. She decides he's obviously stuck dumb so she politely says "Goodbye" and makes a swift exit stage left.
All this boils down to her finding herself being single again. It's not really anything new to her, after all she's spent 90% of her life being single, except this time she's got Jack. To be fair she's not really sure what's going on with Jack. She's hoping that he's had some sort of head trauma making him slightly impaired rather than him actually wanting to have some sort of affair with her. She hadn't even thought about it but really, that's what their situation is. An affair. A secret affair.
When she tells Jenna that she's split with Carol she gets hit by the Spanish Inquisition. She's pretty evasive in answering so she manages to avoid letting slip about the kisses and the affair with Jack. She's pretty sure that Jenna would end up reading far too much into it and decide that it's a great love affair. It's not. And anyway, Jenna has the biggest mouth in TGS (after Griss and Dot Com) and she'd end up telling the whole building about it and Liz is fairly positive that this is something that needs to be kept on the Down Low. Wait. She's totally positive that's what needs to happen because Jacks in a relationship and she doesn't want everyone to think that she's trying to steal him away from Avery. Besides she doesn't want to steal him away, that isn't what's happening here. She's merely trying to react to Jack kissing her; she's not going out of her way to get Jack to kiss her. However when Jack corners her in the depths of the cages backstage she can't help but find herself staring at his lips.
Even when he's asking "Why did you split up with Pilot Carol?" she's remembering the feel of his lips against hers, and the way his hands gripped her hips. That's probably why when he steps forwards and presses her against the wire mesh cages she doesn't put up much of a fight. Instead she finds herself opening her mouth against his and letting his tongue stroke against hers.
It's not love that she feels in her chest, because it can't be. Because she wasn't in love with him before being kissed by him and she's quite sure that his kisses don't have the power to make hapless women like her fall in love with him. Although really, she wouldn't put it past him to be developing some sort of lip balm which has the properties of making someone fall in love with him. Anyway when they finally part, and he tugs at his tie, straightening it, she can't help but feel her heart lurch in a way it never has before when she's looked at him. She convinces herself its guilt, and that the pang of jealously she feels when thinking about him going home to Avery is just indigestion from the meatball sub she had lunch.
She certainly can't let herself thinking about Avery and Jack being in a relationship, nor the fact that they were parents-to-be because then she'd never be able to look anyone in the eye again due to the fear of her being a cheating skank-face.
"Lemon I-"
She pulls him towards her, her hand gripping his tie, and kisses him, stopping him from speaking. When she pulls back she smiles at him before leaving because she can't bear to hear what he has to say. She not sure whether she's more worried about him saying "Lemon I want you" or "Lemon, I can't do this."
By the end of January the kisses are kisses more frequently and she's pretty sure that they're going to end up having sex sooner rather than later. They haven't discussed the status of what they are, in fact they don't really talk at all. They talk about work of course but the kissing is more of a conversation of facial expressions and hand signals. When he hands her an invitation to Avery's Baby shower she smiles and tells him she'd love to go, mainly because she knows it would look weirder if she didn't go.
Jack spends the whole night splitting his attention between Avery and Lemon, luckily Avery's friends are so loud and overbearing they provide the perfect cover for his covert sidelong glances at Lemon. If anyone did look too closely they'd realise that the amount of time he spends with Lemon far outweighs the amount of time he spends near his baby momma. By the end of the night Lemon, Avery and he are the only ones still sober so he's quite sure that if anyone was to notices the dynamics of the evening they'd never remember in the morning. When Avery shows her friends out Jack pulls Lemon into his office/library. He presses her against the closed door, stealing her breath.
When Avery knocks on the door he's got an erection that'd be pretty hard to explain away so he stumbles towards his desk. Lemon just moves to look at the many books lining his floor to ceiling shelves. As Avery enters Lemon makes a comment about the amount of "Capitalist Bullshit Books" that line the shelves and it's enough cover for Avery to not notice the tension or the weird blush on Liz's cheeks. At least he's pretty sure she doesn't notice. Either way Jack replies to Lemon with a comeback of "If everyone had the same Liberal views as you we'd all live in cardboard boxes in the middle of nowhere because no one would be daring enough to invest in building cities" to further cement the ruse of a heated debate.
Avery smiles indulgently at them both and laughs, he smiles noticing out of the corner of his eye that Lemon's face tightens and she shoves the book she's looking at back on the shelf a little harder than necessary. When Liz says she's going Avery offers to walk her down and Jack just nods awkwardly.
By the time Avery returns he's in the bedroom preparing for bed, and all she says is how perfect the evening was. He feels incredibly guilty and knows that what's going on with Lemon isn't right, it isn't honourable, it isn't fair to Avery. But when he lies down and turns the light off all he can think about is Lemon.
He knows he should stop kissing her, he should stop wanting her, but he's sure he's not going to.