Regina can really hold a grudge and as we know be quite vengeful. I think she is going to try and rid FTL of her mother. I like the theory floating around that Regina kills Cora. Maybe that is how she inherits the powers and really becomes quite evil.
I almost feel that Cora would be proud of Regina seeking revenge and becoming darker in character. Like she would give herself a pat on the back thinking “WOW, I taught my daughter well!”