She sounds a little like a sociopath honestly, no regard to how other people feel or how her actions impact them, only a desire to bring people down to her level, and have control.

You need to find a way to catch her doing whatever she's doing in your room, set up a camera, idk. You need to get her out of there preferably with solid proof that she's trying to hurt you/is a danger to her roommates. Because if she does it to you, she's going to do it to someone else. If you didn't throw out the pine Sol facial cleaner personally, I would keep it, buy a new facial cleaner to compare it as proof that it had been tampered with.

I know a girl like that. She constantly would bitch about and cheat on her boyfriend. She would brag to me about how she put "itching powder" in all her bf's sister's clothes because his sister was this terrible person. She would lie about EVERYTHING, to a ridiculous extent that often gives her away. She bragged about how she manipulated her teachers back in highschool into believing that her mother was abusing her at home (her mother is the sweetest and one of the most selfless people I know, ironically, to a fault). She would act very sweet and kind to someone's face, even extremely personable if she wanted something from someone, then bitch about them and brag about how she manipulates them behind their back. She even acted nice to my face, only for me to hear that she'd said I had "spread my legs once and (my boyfriend) welcomed me into his home".

Yeah... Get the hell away from that. She is not your friend.