Wait, broke up? So this progressed to a physical relationship?
As you already realize, thats a self-fulfilling prophecy. You're her emotional crutch, and she's the object of your affections. Just be careful with how much of yourself you invest in this. I totally understand what you're going through. Emotions run hot, shes being "smothered", you want to save her....I get it, I really do, but that doesnt make it right.