Not very good XD Just wrote what came to mind. Lots of GLaDOS quotes

"Thank you for participating in this Aperture Science computer-aided enrichment activity. Goodbye."

Chell's heart quickened as the platform she was on continued forward. Into the fire pit. The flames burst up in an angry plume, dancing around. Waiting for her to fall in so that they could give her her 'victory candescence'. What was happening? She had finished the test, right? Why was her guide doing this to her? She had told her everything was going according to plan

Unless this was the plan all along.

Sweat ran down her back and stained her uniform. This was it. This was why the computer had been acting so strangely. Saying things like 'you are going to be missed' and 'you will be baked'. Chell had assumed that it was a glitch in the systems or the AI was just programmed to speak in riddles or something. Not this. Not this at all. Of course, Chell wasn't really sure what AIs were supposed to act like anyways. She couldn't remember that.

She couldn't remember anything, for that much.

When she had woken up in the Enrichment Center she had found a small file in the room. It simply stated her name, 'Chell', and some words she didn't understand describing her abilities and disabilities. Something about why she had these strange robotic braces on her legs. No matter how many times she read over it it all went over her head. But it told her one thing: apparently she had signed up for this. She was a volunteer. Considering that she couldn't even recall who she was, she had believed it wholeheartedly. It filled up some of the empty space in her memories and she had hoped would help reconstruct the others.

She wasn't so sure anymore that she had been a willing participant. Who in their right mind would want to do this?

The computer, her guide, had been so helpful throughout this whole thing. Well, in her own special way. Sometimes the advice had been well put, while other times it was wry and slightly sardonic. Okay, more than slightly sardonic. Making death lower in intensity than a bad mark on an official record was a prime example of that. Telling her that it was a normal side effect to taste blood. To lose teeth. To have schizophrenia and hallucinations. Calling her an android and throwing her into a room full of turrets waiting to shower bullets into her body.

Even through all this, Chell had trusted her guide. The computer had encouraged her, rallying her spirits to keep going. To finish the test. She had even added an incentive: a freshly baked cake when everything was over.

If Chell had been paying attention to the writing all over the chamber walls, she would have noticed the obvious warnings to her guide's true motives: 'The cake is a lie'.

But she hadn't. She had devoted herself to doing the best job possible. To completing the test. To pleasing her guide. And so, she did everything the computer told her to without question or reason. Everything the computer expected of her.

Now that the computer was expecting her to burn in a fire pit, she wasn't sure how obedient she wanted to be.

The flames were licking up against her, blistering the skin on her exposed feet. She didn't have much time. Soon she would be too close, and the fire would kill her. Four thousand degrees Kelvin? No chance of surviving that. Too bad she also didn't have a way out…

Wait! The portal gun! She looked at the device on her right hand that had been the cause of all her troubles with newfound affection. She would use the computer's machinery against her. Her guide had even said herself that this technology would still work with this heat.

Chell desperately looked around, searching for a means of escape. There! Above the pit was a small ledge with white tiles. The tiles that could sustain a half of a portal. She shot a blue one on the ceiling above it, surprised at how naturally she could aim and use the device. Then she turned to her side, plastering the other orange half on the wall next to her. As soon as she saw the ledge through the doorway she had created, she knew she could make it. She was not going to die.

She was about to go through it, to safety, when her whole body froze. Something about this seemed horribly wrong. What if this was just a part of the test? What if the computer was trying to see if she would follow her instructions to the end? The flames were not real. She was just simulating them so that Chell would be faced with this decision. When she didn't try to run the fire would shut off and Chell would find that there was nothing dangerous there at all. Instead a cake would be waiting for her. Maybe her friend the Companion Cube would be there too. She sure missed her…

It was then Chell realized that she might be going insane.

She made her choice based on that.

Closing her eyes, facing the portal, she jumped through.