I don't think Mellie really likes anything. I don't really think she even loves Fitz. Not really. She loves the power that comes along with being First Lady. I think she had children because that's what is expected of a political wife and I definitely think she got pregnant again as a manipulation. She clearly didn't care about the health of that baby, since she had the doctor induce early.
Of all the schemers on this show and people with questionable morals, Mellie is the worst. I don't even think she cares if Fitz is happy or not. It's only about winning.