Chell is the tenacious lead character of the Portal Games, but I was wondering why out of all the former employees of Aperture Science was she picked? Was she just the last survivor, or was there a reason she was brought of stasis?
According to the psychological profile in her personnel file, Chell is "abnormally stubborn" and refuses to ever give up, no matter how daunting the challenge. Originally, she was rejected as a test subject, but Doug Rattmann. altered the testing order, having correctly guessed that Chell's extreme tenacity might allow her to defeat GLaDOS.
You could freely and legally read it here. You could see the flashback of Chell's selection on page 21 and the alteration the testing order on page 22. The details of her personnel file are in page 27.