Same thing just happened to my, now roommate. Almost 4 weeks ago, his girlfriend gave him the "I need time to myself" speech. Two weeks later he finds out she's back to her old ways of drinking, smoking, partying, etc.. Finds out she made out with a chic at a party(I know, not ALWAYS a bad thing!

), but it was just to impress a bunch of dudes. She went down to Florida by herself to hang out with her friend that lives down there. She evidently went out partying and dancing with guys, and pretty much everything she WOULDN'T have done if she was with my buddy. In the meantime, he's been worried sick(literally) the whole time, and get this..... paying 1/2 the fuggin' rent at their apartment!! He finally worked up the balls to go pickup all of his stuff and move it to my house, but he can't stop calling her and talking to her. Hopefully your situation works out for the better, as it's obvious you're pretty heart broken over it. I do think it's time to move on, and a couple months down the road I think you'll be happy with your decision.
Mark