henritje said:
Portal 2 is set MILLIONS of years after Portal 1 (which is set somewhere after HL2 like GLaDOS said in P1 "the world has changed")
maybe the Borealis but not Chell
They actually never state how much time has passed since Portal. Were it millions of years there'd have been nothing left of the Aperture facility. I'm not saying that alot of time didn't end up passing but I would reckon it's more on the order of hundreds rather than millions.
@OP, Chell doesn't have brain damage; Wheatley only says it was a possibility she could have brain damage. She's also always been a mute; that didn't just start with Portal 2. It's just actually acknowledge by the characters around her.