Left to...
Chell was gone.
GLaDOS was walking through the quiet facility. She had let her go, and now that there was no one left to test with...
A sound the android had never heard herself make before escaped her mouth. She was sobbing!
'There's nothing I can do now,' the android thought. 'I let her go. That stubborn arrogant, smug little woman... I should be glad to be rid of her...'
Another sob escaped GLaDOS mouth. She covered her face with her hands and stopped walking. 'She was the perfect test subject... she was my friend...'
The android's knees gave way under her and she found herself on the ground.
"I loved her..." she whispered. "And she never knew..."
GLaDOS felt a stabbing pain in her chest. She looked around the facility.
'There's nothing left for me to do here...'
She got up and walked to the elevator, taking it to the surface level. She smiled a sad smile and whispered, "Goodbye, Chell. May you live happy and well." Then she released the brakes of the elevator and began to freefall to the bottom of the facility in it.
Also uploaded this on my gf's and mine chelldos tumblr ( .com), though there's like almost nothing on there yet. xD