My opinion isn't worth much, but here it is.
Back when she liked marriage for a man and a woman, she was married to Bill and having boy friends such as Vince Foster.
Now she is rumored to be involved with Huma Abedin, and according to Genifer Flowers she has been with women before.
Changing your views will change when you change who you have sex with.
It also doesn't hurt to go with where the wind is blowing. Hillary is famous for that.