My own guess is that she probably had a mix of reactions. She probably both liked and loved him to start with. Still loved him in a way but quite over him (?I think that's probable) in many other ways as time went on. Stayed for reasons I don't say I understand (perhaps vows even when he'd repeatedly not followed them), and her own calculations about what she wanted to do herself in political life. Whate'er is good or not so about her, I take her as able to calculate, so, as I said, it may have been a mix - of remnants of love and thoughts of her own role in politics.
It's hard to see into the heart of other people's marriages, and sometimes harder to see into your own.
I have a good friend who is quite the bold/aggressive woman, very capable, also attractive. She has stayed with her husband (whom she has strongly railed about to me, and, ha, to him.) She stayed because she said she would. That was their pact. In her case, infidelity wasn't going on, but anger could get huge.
I don't think feminism, whatever it is, and people describe it in many ways, equates with leaving a husband over fidelity. It may for plenty of women but feminists aren't cookie cut.