Andrew
I'm sorry for your loss.
I've had many such losses - not all girlfriends who I thought I "loved" as such, but I often reflected on the fact that it was the hope of a perfect relationship which I was mourning rather than the girl/woman herself.
If this is the way she treats you, you deserve better. You have been clear with her about your feelings and consistent in that. She has not.
Do you really want to be with someone who has done this to you? She may have been great to be with for a while but to be with for some time/forever, you need to have more trust than you can now have with this girl, so my advice is:
Realise that it hurts
Ask yourself if you would REALLY want her back
Consider if you are mourning the hope not the girl
I hope this advice helps and I know what your pain feels like. It's not every boy/man who can talk about it and you have. That makes you one who women will appreciate in future. Hey, you've got a date already!
Big hugs (in a straight, manly way, in case you think that's weird!)
KP