I am a little curious how the heck [Name] got isekai in Resident Evil in the first place. I have few ideas:
• They have a friend who is a crazy genius who is obsessed of "THERE'S A WAY TO GO TO ANOTHER UNIVERSE!" and uses Resident Evil as an example and uses [Name] as a test subject for their experiment, they got bribe for it. It went wrong since originally, their friend was gonna get them out after Re2 but the machine gone haywire and it took a lot of time to finish the machine while maintaining [Name]'s physical health to make sure it functions perfectly after they transported her back. To make things clear, [Name]'s mind was transported in Resident Evil and her physical body is left behind.
[Name] talking to air: "Okay, [Friend's Name], time for me to leave this game, I'm mentally and physically tired."
[Friend's Name] talking to her in her mind: "[NAME]! We have a problem! The machine is going haywire! You're stuck in that place. So please bare with me and I'll get it fix."
[Name] staring at the air in disbelief: "WHAT!?"
• An entity, bare with me, is bored and decided to transport [Name] in Resident Evil. After RE6, they bring them back since they got bored and Leon is not in the rest of the games (The entity is entertained by Leon's feelings for [Name]) and then put them back again after RE: Requim got released.
[Name]: *doing something*
Entity: I'm bored, I'm using this mortal as entertainment. *Snap finger and [Name] is in RE Universe*
[Name] got transported in a middle of an apocalypse: What the f-
• [Name] soul split. One in the real world and the other is in the. The whole adventure in RE is like a dream to the Real world, it did cause her to have headaches every morning. How did it happened? The same entity in the 3rd one.
[Name] waking up after RE6: Holy shit it was a dream thank god. I think I need Therapy.
[Name]: Oh right, I still have bills to pay... Hooray.
But I'm also curious, does the RE universe a game to [Name] because she's from the real world and the RE universe is an actual reality to the characters? Because if it is that explains [Name]'s never aging thing, because she's an anomaly.
I didn't actually intend to give [Name] a specific background because I wanted the reader to use their imagine and created their own backstory like Yuu in Twisted Wonderland. Sometimes, authors arbitrarily give readers a sob story, family, lover and friends which makes me lose interested pretty quickly.
Your idea is pretty cool tho ^^