good to hear you have a good support system at home, imo forget her, not her in general, just the notion of ever being with her, ever, it just doesn't sound like it will ever be happy, and as everyone is saying, at least it happened b4 you both got tied down with a kid or two, which will haunt you for life. (kid of course would be loved, but no the battle) now you just have to fight over some cd's and at most a couch.
when in doubt, just let her have **** and be done with her, don't ever let her "come back" for **** and more ****, also if she does, don't ever let her come over, it's your place now, if she wants anything just drop it off at her sisters place and leave.
again i actually haven't experienced this personally, just seen a few friends and thought about the "right way" to just end it.