@RedOnYellow
I think
you misunderstood something. The girl that was in the simulation was called Ayame, then when she talks about her big sister and is reminded she "doesn't exist" anymore, she says the name Asebi while looking sad about it, at which point it cuts to Asebi still existing.
I don't know how you took it that way, because it makes way less sense if that was just some random shot of Asebi's backstory out of nowhere, considering that she had zero experience living as a human at first and if that was some backstory of her having a dead sister whose name she stole it's a real weird time for that backstory to come out. I guess I can see where that idea comes from, since it centers on the the headset in the panel where she says "she doesn't exist anymore," but that interpretation doesn't make any sense considering the names and the timing of the scene transitions, and making the assumption that time is processed quicker in the simulation makes sense from a computing standpoint but is still a pretty big leap for something the manga never stated.
Of course, being robots neither of them can have "biological" sisters unless humanoid models have some organic bits we don't know about, but I'm sure it's something to the effect of the "father" wanting these android girls to live like humans. He probably sent Asebi out into the world and assumed she died in the ship crash or something, and is taking the safer method of training her "little sister" Ayame with simulations where she can't actually get hurt. With it being "all thanks to her (Asebi)," maybe it's also possible that she was wirelessly and unknowingly transmitting data about the modern human world so they could build the simulation, and they think Asebi "no longer exists" because they lost the signal, or not being around is the same as not existing to them, or it was a weird translation, or whatever. Maybe Asebi
was also recreated in the simulation, so Ayame was sad upon leaving it because her big sister wasn't around anymore, but that still doesn't mean that it was Asebi herself because then the scene and its placement still make no sense.
Regardless, you could speculate a hundred different things about that snippet from last chapter, but I don't think in any way it that Ayame and Asebi are the same person. If that was supposed to be Asebi's backstory then it was way too vague, misleading, and poorly timed, and this author has been way better about presenting information so far.