And here we are into the next arc, which I have dubbed:
SP/dr!
(Yeah, I couldn't find an original story arc that had SP/dr in the name, so shush don't tell anyone.)
When Mei arrives in her assigned universe, she finds it to be in absolute pandemonium.
The Anti-Venom hordes have already invaded.
Mei is forced to fight her way through the futuristic city of Nueva Tokyo, helping the advanced heroes such as Daredevil, Kamala Khan, and Thor fend off the Anti-Venom zombies in their efforts to strive off the invasion, all the while battling her way to the centre of the city to reach her target.
And soon enough she finds them.
Them being Peni Parker, piloting the SP/dr mechsuit.
After Mei stops geeking out about the SP/dr mech and begging to know how it is made, she begins to try to explain what is happening to Peni, only for Peni to reveal that she already knows what's going on. She was the one who helped the Inner Web develop their Web-Watches after all.
Peni's already done her part in assisting the Spider-Army, but when Mei reveals to her that she needs to leave to join the army proper - highlighting her importance as a Spider-Totem - Peni is much extremely reluctant to leave. Her entire universe is in danger. She can't abandon it in its time of need, especially when there's the possibility of a weakness in the Anti-Venom hordes to be found. Mei tries to argue against this, but can't help but want to see Peni succeed in this matter, especially if there is a real chance of there being a weakness to exploit in the army of Anti-Venoms, so she decides to stay and help.
Mei and Peni begin their work, capturing as many Anti-Venom zombies as they can and trying to figure out what their weaknesses are. However, Mei grows more and more concerned with how absorbed Peni is with her work and how much she is disregarding the needs of the people that she is talking to in favour of pursuing her scientific desires.
However, Mei sees way too much of herself in Peni to just abandon her to her own projects. Peni is so much like she was just two years ago, young and bold and eager to invent and create, but with not much in the way of regard for other people and how they feel. Mei does not want to leave Peni here if she can help it, and resolves to be the conscious that Peni needs to keep doing the right thing.
This arc is meant to be the culmination of Mei's character development. At the beginning of the story. Mei is supposed to be characterised as incredibly apathetic to the people around her, her only desires being to invent and create new devices regardless of the concerns of the people around her. However, over the course of the story Mei learns how to talk to and relate to those she is surrounded by, think about the world outside her bubble, and come to truly care about her friends, which ultimately leads to her becoming Ironheart and taking on Momo as her girlfriend, having truly come to cherish the people she loves. Now, while Mei still does possess her curious heart and her desire to invent and create (that hasn't been diminished and is still a key part of her character), it has been tempered by her care for her friends and her desire to see them all safe and sound, hence why she has taken up the mantle of a hero.
Peni Parker, by contrast, is exactly who Mei used to be at the start of the story: someone who is so invested in their work and unable to recognise the thoughts of those around her that it leaves her feeling apathetic to how they feel.
So, Mei resolves to be the angel on Peni's shoulder, helping to keep her on the straight path and remind her that people exist outside of her and her inventions; people that care about her and want to see her safe beyond her creations. In doing so, Mei becomes an older sister figure to Peni, who comes to cherish her company in her own way.
However, Peni's efforts prove to be in vain, as there doesn't seem to be any sort of weakness that the Anti-Venom zombies have. Fire, sound, none of the regular weaknesses that Symbiotes across the multiverse have are affecting the creatures. She even starts pushing for potential weaknesses outside those areas, and even though she seems to be making some progress with electricity, it's not enough to make a major difference...
And then it all goes wrong, as the Anti-Venom zombies in captivity manage to escape and begin infecting the entire facility that they were store in, infecting not just Peni's only friend Addy Brock and her VEN#n suit, but the brilliant scientist May Parker and the M.O.R.B.I.U.S. kaiju that had been stored underneath the building for study as well, creating a great disaster as Mei tries to evacuate as many people from the facility as she can whilst Peni is forced to battle against the infected VEN#n and Addy, desperately trying to save them to no success.
Even worse is when one of Cindy Moon's generals, Elaine Coll, now calling herself Lady Scorpion, joins the fray alongside her Anti-Venom Nomu guards, forcing Mei to personally take her on to protect Peni and allow her to evacuate. However, when Lady Scorpion lands a poisonous blow on Peni when she is trying to save her research, Mei is forced to break off the fight and drag Peni out of the facility as it is overrun with Anti-Venom zombies and wrapped in flames.
At the end of it, Peni and Mei sit atop a damaged skyscraper and sombrely watch the whole of Peni's world being consumed by the endless swarms of Anti-Venom monsters. The entire universe has been consumed, and the only thing that they can do now is flee while they can.
But before they do, Peni shares her story with Mei: she'd grown up with her Aunt May and Uncle Ben, a brilliant scientist and soldier respectively, since her parents died when she was young. May had been the one to develop the SP/dr suit and the radioactive spider that acted as its co-pilot, and Ben had been the one to pilot it, acting as this world's first Spider-Man and protecting the city of Tokyo.
However, one day Ben was murdered. Not in a battle or by an archnemesis, but by a simple mugger on the street ambushing him on his way back home and stealing his wallet. It was an utterly undignified end, and in a fit of rage, Peni had taken control of the SP/dr mech, finding the man who had killed her uncle, and beating him half to death. It is only because of the bond that the radioactive spider had created with her and its telepathic words reminding her of the hero that Ben had been that she had spared the man's life.
From there, Peni had become absorbed in her work, obsessed with creating as many inventions as she could whilst also piloting the SP/dr mech, having already bonded with the spider inside whilst having similar enough DNA to Uncle Ben to facilitate such a bond, all so that she could make sure that no one would ever have to suffer such a fate or lose any of their loved ones ever again.
And now... now look at it. Her world was lost and it was her fault.
Mei swiftly shoots this down. Peni has made some mistakes, but that doesn't mean that it's her fault. It is Cindy Moon and her generals that are to blame for this madness. And Peni has already helped the Spider-Army in their battle against the Anti-Venom hordes with not learning that the Anti-Venom Symbiote had a possible weakness to electricity, but the Web-Watches as well. Without her, the multiverse would've lost this war a long time ago.
And, well... Mei was never close to her parents. They never really tried to raise her, so Mei might not understand Peni's loss as well as she could. But she does understand the need to make up for the losses that one suffers, the desire to create something new no matter what. She understands that deeply, and advises Peni never to let go of that desire, as it is something pure and beautiful.
But... allow the people in her life to see her for who she is, and to let them show her as well. There are people out there that care about her. Don't force them away. Keep them close and cherish them.
Allow them to let her see the true value in what she makes.
The portal opens behind them and Mei ushers Peni inside, telling her that they still had a chance to save not just her friends and family, but everyone else as well.
Peni, within the SP/dr mech, walks through the portal, followed by Mei shortly after, leaving behind the doomed world and its doomed souls...
All while Elaine reports back to Cindy of the news of the growing Spider-Army.
I'm wording that, whilst I was writing this, I framed Mei and Peni to have some form of social disorder and treated it as if it was a bad thing.
They don't, and it's not.