I will start with a list of grievances.
(1) You continually lock me out of my own bathroom. Three times a week is too often for you to “forget” to unlock the bathroom door that we share, and if you really are that stupid, write yourself a note or something, you whore.
(2) Those long black hairs you leave on the bathroom floor. I know it’s from your head, but I’ll be damned if I will live the rest of this year peeling black hair off of my bare feet while I curse every inch of your stupid, cheap-perfume-scented body.
(3) You used my soap. What, did you think I wouldn’t know it was you? I don’t use your candy-scented bodywash (because I’m not 13).
(4) Your voice. It’s awful.
(5) The following sticky note that you left on the bathroom mirror: “I almost wish we were butterflies and liv’d but three summer days—three such days with you I could fill with more delight than fifty common years could ever contain.” I don’t know who initially wrote this, but those words are as repulsive to me as dead puppies. Fuck you.
Now that I’ve stated my grievances, I’ll tell you what’s going to happen next. I’m fucking evil. That cereal you always eat? Whenever I sweep, I will put the dirt into your cereal box. I will rip your laundry into pieces while it’s still in the dryer (“Our dryer is awful!”). I will put nail-polish
remover into your shampoo.
I will rip out the last pages of every book you are reading. You have been warned. 
I have a great idea. Instead of being an adult, why don’t you commit crimes over hair on the floor. You could put non-edible things in her food – you might find this is considered poisoning or assault, depending on where you live and the criminal statutes. You could pour toxic chemicals into her shampoo that run the risk of blinding her, which is also assault. You could damage her property, which is a criminal act.
Or you could get some fucking help before you’re court ordered to.
How do you know she used your soap? Do you mark lines on the bottle? Do you take pictures of how much of the logo is still imprinted on the bar? Bar soap fucking melts in the shower even if *nobody’s* using it!
Also, I wouldn’t be surprised if she “accidentally” locks you out of the bathroom as passive-aggressive punishment for you being fucking psychotic.
Jeez, I would trade the hell-bitch I lived with for two years for this ditz in a second, if that’s the worst list of grievances you can come up with. I would happily share my soap to escape the non-stop parade of idiot “boyfriends” (read: new roommates)
Yeah, your roommate doesn’t smell good to you and leaves her hair on the floor, but she has to live with a passive-aggressive bitch. So who has the worse end of the deal?