The fact that you seem to believe she should give you a chance is part of the problem here. Attraction just doesn't work like that. Attraction frequently has no rationale. It can be hit and miss. And most of all, it's instinctive - not something which we have to make a decision about. I've had men who's attraction I couldn't return. And I've liked men who weren't interested in me. However, there is never an expectation that anyone should push themselves to find that attraction.
It's great that you've done a lot of self improvement - but put your efforts into women who are interested in dating you.
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.