I don't really understand. You weren't together, were you?
If you weren't together then who really cares, she's with YOU now. This says more about you than it says about her, insecurity?
About the other guy, he sounds like a jerk and he's just pushing your buttons - apparently it works too. Ignore him, you're with her and he's not. Who cares.
To love is to suffer. To avoid suffering, one must not love; but then one suffers from not loving. Therefore, to love is to suffer, not to love is to suffer, to suffer is to suffer. To be happy is to love; to be happy then is to suffer, but suffering makes one unhappy; therefore to be unhappy one must love or love to suffer or suffer from too much happiness. I hope you're getting this down.