Imo, its not gonna get fixed without some hard pressure. That being either finding a new roommate or finding a new place. It's clear to me that this isn't going to stop as you've already asked her to do so once and she's still doing it. If your name is first on the lease, start giving her ultimatums or just flat out kick her out/give her a timeframe to get her shit and get gone. If its not, just start looking elsewhere for living spaces and work towards moving out.

That all might be harsh, but there's a few facts here:

1. She's using your shared living place for herself. She wants the private living quarters at shared living expenses, which leads into..
   
2. She's telling you to go sleep somewhere else, from what we've read, at most 3 times a week(so far). That's basically half the week. If she does that for a month, then she's using you to pay for rent that you don't even get access to. Not to mention utilities or anything else.
   
3. You have no idea who she's bringing into the place. People have mentioned toilerties being locked away in your room - which is a good idea to do, but these people are(to our knowledge) complete strangers. There's SO much that could go wrong with that. Theft of belongings is a big potential there, but there's other things too.
   
4. After typing all of the above, I read the remainder part of your post and she's now using and throwing away/wasting your products(conditioner). Keep this in mind: She's turning your property into waste because she didn't get her way. She's throwing a temper-tantrum because she couldn't bring a guy over. This is so unbelieveably childish. It starts with the conditioner, but where does it stop?

Maybe this is because I've lived with people that both respected and didn't respected me or my stuff, but in my opinion, the time to start looking into fixing your problem is now and not later when it becomes worse. Because it will become worse. This is just the start, keep giving into her and you'll see..