I’m curious, her child with him is young enough to be breastfed? And you have a child with him also? Are these two children close in age? Maybe she is doing it on purpose, because (and without more info from you) she has a very young child with him, and he left her for someone else. He abandoned her and his child. I’m pretty sure she has more reason to dislike you than you do her. Also, you even said it yourself..your fiance is with you and not her. If he wanted to be with someone, it sounds like it’s not just because of the boobs, it’s because he actually loves you. After having a child, my boobs changed.. my husband may miss my old boobs, but he still loves the ones I have.