"
And believe me I am
still alive.
I'm doing science and I'm
still alive.
I feel fantastic and I'm
still alive.
While you're dying I'll be
still alive.
And when you're dead I will be
still alive
At the end of test chamber 19, when GLaDOS attempts to kill Chell by lowering her into an incinerator, she specifically says, "All Aperture technologies remain safely operational up to 4000 degrees Kelvin." As GLaDOS herself is Aperture technology, it can be assumed that she, too, is heat resistant, and did not actually die when thrown into the incinerator by Chell.