Have a long hard think about it and take your time to decide if you actually want to be back with her and legitimately regret things or if you are in love with the idea of being back with her.
When I broke off my 5 year long relationship, I couldn't believe it. I regretted it so much and thought perhaps I was a fool... I thought I had made a terrible mistake. But I knew we weren't right for each other in the long run, our time was up. I decided a small part of me would love her forever but not in the way I love a significant other exactly and it is only a small part of me... and that what I was struggling with was that I still loved the idea of being with her, and that the emotional response was more to do with looking back on the good times we had together and wanting something like that back and feeling a fondness for her still. It was a difficult realisation for me to have but once it sunk in that I didn't actually want the real her back I just wanted what we once had, it became much easier to let go and move on.
Maybe it's nothing even similar for you, maybe it is...
If you decide you do genuinely want her back in the end, tell her exactly what you told us, both the positives and the negatives.
If you decide you don't want her as she really is, maybe this will help you with closure.