BA: wow! Wouldn't that be funny if after all that dating you ended up with your former GF? Maybe you needed to go through all of it to come to the right conclusion. Of course, right now you really need to step back & remember why you broke up with her in the first place. Unless those issues were resolved - you could quickly end up in the same place which obviously was not working for you.
Lots to think about. But nice you and she could enjoy some time together.