You are a fool. Is this reasonable for you? She is a fitness instructor, and her career determines her social scope. She will meet many people, including male friends, and will meet many. It is normal for her to have several suitors around her. You have no reason to blame her, let alone forbid her to associate with other men. So, what you did was very irrational.

As long as you are not married, other men can pursue her. This is someone else's right. There is nothing wrong with liking someone. Therefore, any unmarried man in the world can pursue her. This is no problem. You're the one with the problem.

So, if you don't do this, your relationship is ruined. Therefore, it is true that it is impossible to continue and cultivate feelings well.