I have played through Portal and found several references that somewhat point to the fact that Chell may be an android.
GlaDOS says “Well done android…”
and “Android Hell is a real place where you will be sent…”
Chell does not say anything like Atlas and P-Body. (this may be excused by her brain damage due to suspension)
Chell is an “orphan” and there by has no record of parents or family.
Cave Johnson says that the repulsion gel does not interact well with the human skeleton, but Chell gets covered in it and appears to be fine.
The Moon Rock gel is supposed to be extremely toxic since it appears to be killing Cave Johnson. Again Chell is covered in it and is fine.
So, is Chell an android?
No, I doubt it. Regarding the first two, in the training chamber you go through, Glados states that the normal Chamber 16 is down for maintenance, so Chell instead is put through a training course for military androids (which is why there are so many turrets in there.) Those lines are simply her trying to manipulate the androids that normally navigate said chambers.
As far as the last couple go, the Moon Rock gel probably didn’t kill Cave johnson in a single day. It’s more likely prolonged exposure that gave him said poisoning. The repulsion gel is a bit less clear, but perhaps it was a prototype version that “does not like the human skeleton”, or maybe Chell’s somehow immune to it. For example, IIRC we know Chell’s the only one out of however many humans put into stasis to actually survive, she’s not exactly an ordinary test subject. It’s not completely explained, but there’s various possibilities.
Finally, there’s plenty of things Glados says that point to Chell being human. For example, she was put into stasis like a human, and certain comments (like the ones about her being fat or Glados mocking her about being an orphan) just wouldn’t make sense if she was an android. Not to mention, I believe that in the one room with the various potato batteries children made in Portal 2, one of them is marked as Chell’s, which would undoubtably prove she’s just a normal human. So, long story short, there’s no real reason to believe Chell’s an android, and plenty of evidence to the contrary.
And one more point that I almost forgot.
What kind of android can eat cake?