Why does glados want to kill chell

GLaDOS has been taught to do nothing but science. To perfect science, if you will.
GLaDOS does not want to kill Chell... she's researching on Chell, to help science.
In a way, GLaDOS is trying to help Chell. Chell is schizophrenic. Despite the passive aggressive behavior of the supercomputer, you can tell that GLaDOS and Chell do seem to have some kind of awkward relationship.
As far as I know, GLaDOS likes Chell.
I believe Valve was trying to say that GLaDOS sort of loved Chell.
Why would GLaDOS bother with that? More proof is that GLaDOS could have easily killed Chell in one of the testing chambers.
GLaDOS has no motivation to kill Chell.

EDIT: Except at the end, GLaDOS wanted to kill Chell, saying Chell "Broke her heart." By then, though, Chell is teleported out of the Aperture Science building, and GLaDOS is immobilized.

EDIT: Chell never escaped. She was taken back into the facility by the Escort Bot. GLaDOS was researching on Chell for science. Since Chell escape from the testing course, GLaDOS tried to bring her back, but Chell wouldn't return. I'm assuming that since GLaDOS didn't know what Chell was trying to do, GLaDOS got frustrated (maybe even scared) so she tried to get rid of Chell before she could do anything. But Chell "killed" her and Portal 1 ends. In Portal 2, GLaDOS is accidentally turned back on by Wheatley, and makes Chell test all over again. While the latter is testing, GLaDOS explained her new resentment on Chell: GLaDOS was programmed to record the last minutes of her death in case something should happen to her. When she was "killed" she was forced to expirience Chell murdering GLaDOS over and over again. So we obviously see why GLaDOS is trying to kill her. But she prolonged Chell's death, so I think that GLaDOS was trying to torture her before she killed Chell.