Why wouldn't she just fake it by talking in a hoarse voice rather than actually damaging her vocal chords...

You'd think she'd spend the two hours preparing for her oral report unless she's got social anxiety, which I doubt since she has no reservations about doing this. It's still early enough to put in for a change in roommate, as others have suggested. In the meantime, how about going to the library and doing your work there. Best of luck!

Perfect logic.

Why scream? All you need to do is sing along to loud 80s music for an hour. Tested and proven to blow out your voice.

grab a hand full of pepper powder and shove it down her open mouth

And speaking as a college professor ... that's probably not going to get her out of it anyway. If it was one of my students, I'd just have her do it a few days later. Stuff like that might work in high school, but not in college.

you should keep a mirror in front of her to show how horrible she looks when she screams

Or... She could just skip the class.

throat punch her

record her and send the video to her prof.