Nope, it's convenience. She likes the life of a Senator's wife, and does not want to give it up.
Otherwise, she would not have said what she did.
Except, he wasn't even a senator when she said that. It is entirely possible that, faced with the situation in real life, she takes a different opinion.
I for one, respect the woman for not just giving up on her marriage and honoring the vows that she took. Do you expect her to divorce her husband (and break up a family with four kids), just for the sake of being consistent with a statement that she made in response to a hypothetical question posed to her seven years ago?
Bottom line...she's using him just as much as he is using her. Textbook marriage of convenience.
I feel sorry for the children.