Girls..help.ex gf seeing someone else? move on?

I'd been with my ex for almost a year, both our longest. We love/d each other. She told me she loved me more than anyone she's ever been w and i knew i wanted to marry her. it got too serious and she freaked and we broke it off a couple of times only to have her return telling me how much she missed me.i invited her to live w/me and my roomie cause she was desperate for aplace.since, i get the feeling she was interested in someone else.last week, i needed to get a # from her phonebook and i saw a txt from a guy i didn't know who she sees through friends often.i couldnt resist and read it.it said something like "hey sweetness, hope you're sleeping well and dreaming of me".i knew she'd be furious as she was when i told her but she swore that although he liked her, they were only friends.she said she was moving out (tho since she said she wanted to stay). i wrote her a note saying i loved her but for now i was done fighting for her.next day i found old loveletters from me in the trash.