Hi Joe!
First I would take a step back. There is no rush to make an important decision. When you don’t have an answer, for me then one is not possibly available yet. How does your fiance feel about trying again? What are her expectations? What kind of physical attraction do you have to the new girl? Is there chemistry or is she just really nice? You have to first be really honest with yourself, not only about what’s possible but also if it could work again with the fiance . Are the problems that you once had fixed on an individual level? How do you know? Could it be possible that maybe neither of the women are meant for you next relationship?