Who is the character you play in Portal?
Solution 1:
She is Chell.
See here:
Although Chell's origins are unknown, she was most definitely among the people present during GLaDOS's activation in 200-, as GLaDOS locked down the facility after her activation, letting none escape, or be let in from the outside.
EDIT: Visiting aperturescience.com, you can learn that she is the daughter of Cave Johnson (CEO of Aperture Science) and that she was brought there on Bring Your Daughter To Work day.