Best way I've ever seen this situation handled was a guy changed the locks on the house, and informed her (it cut out any posability of her getting a copy of the key made before returning it to him). When she came home, he reminded her she didn't live there anymore because he's only looking for people who stick by their word, and wanted her old key returned and to establish a date that would be best for her to rent a uhaul and remove all of her items from his house, because he didn't want to have to go through the court system, and wanted to remain civil. I have to admit the whole situation went over really smoothly because dates and terms were set and agreed upon. He wrote everything down and they both signed 'the agreement' and so they were both accountable to the other on dates and times. I think your biggest thing here is to kind of do a similiar thing. You're the guy who owns the house and should be in charge, just set terms/dates and expectations on those terms/dates. No reason you guys can't get out of this and still be friends in a few months, don't expect to go out for beers next Friday though, and make it very clear that once she is out there are no second chances, because you know second chances turn into third, and fourth, and fifth, and so-on, which is not conducive to a effective relationship so you don't want to even go down that road. You'll find someone else because you're going to be fine.