You are completely justified in asking her to move out, especially since everything is under your name and it's your butt on the line. She should be old enough now to not be playing games, and your requests are not unreasonable. You'd really only be paying 1/6 more, seeing as you and your bf would be splitting her third, right? And since she's always at her bf's anyway, tell her she can move in with him.
I'm kidding, don't really tell her that. But you need to stand up for yourself.
Edit: I have four friends that lived together and did a weekly chore revolving list. One week garbage, next week kitchen, next week bathroom, etc. But that wouldn't solve the problems like leaving the oven on all night.