I'll tell you straight away - I'm not going to baby you here.

The hard truth is that this is YOUR problem, not hers. Your actions have a slight stench of jealousy and insecurity.

This is her problem. It's part of her past. Yes, it's someone she used to be romantically involved with, but it's also someone who had done great harm to her. She wanted to have a better understanding of why he did what he did so she could have a better grasp on her own life moving forward.

If she gave you any real reasons to worry, then you might be justified in bringing this up with her and how it makes you feel. But she's been open, caring, and trusting with you about this. Instead, you chose to act in a way that reflects how you might behave in future situations. For a couple considering moving into the "serious" territory, this would weigh heavily on my mind, and should on hers.

I don't think you deserve her.

You should work on your own self esteem, maybe talk to a therapist, and learn how to trust people when they tell you the truth instead of trying to control them.