Ok so the curse Regina wanted to use on Henry makes someone think they love you. Is it possible that Cora used that same curse on Regina at one point? Cause honestly even though that is her mother, after all the pain she had caused for Regina there is no way love could be there. It would explain why no matter what Cora decided, een the things Regina was completely against, she went along with it. Maybe Regina will realize that and that will help her heal and thus allow MM to heal as well.