This is not going to happen.
Instead of flaming you and calling you a fucking idiot for asking us to do something illegal for you when we clearly state
HackThisSite does not support illegal activities.
on every page, I am going to give you some personal advice:
Let it go.
If you don't trust her now, you never will. First it will be tumblr, where all sorts of drama goes down. Then you will start to wonder about her facebook. Then email. Then before you know it you wanna root her phone and have all text messages forwarded to you. I've been there, and after a while of doxing people close to you... you start to feel like the shitty person you are.
Just talk to her. This is not a problem that technology can solve. This can only be tackled by being open and honest about how you feel. I know it sounds lame and whatever, it is. But believe me when I say you are either going to find something that will hurt, or you will find nothing and that will hurt more. God forbid she finds out you read her journal.
It hurts to admit it, but she might not be the one for you. Or maybe you're not right for her. Maybe you're so self-conscious that you will never feel secure with anyone. That happens, but there's not a hack in the world that can change who you are.
Trust me. This is not a path you want to go down.