she always said it was a court issue. so, she was always consistent in separating her own opinion (which was opposed) to the official position (which she claimed was out of her jurisdiction). the actual truth is that she still doesn't support gay marriage, on a personal level. but, she acknowledges that the court has made a ruling, and that's the correct legal mechanism to work it out through. she sees her role as upholding the rights determined by the court, not contradicting it.
now, you can dissect that all you want. if you want to believe she's a gay advocate, you argue that she supported it all along but held back politically. if you want to believe she's a fundamentalist methodist, you argue that she's just cynically phishing for votes. fwiw, i think the second option is more correct.
but, the truth is that there's really no flip-flopping. there's a consistent message of it being a court issue. as the court has changed, she has shifted to reflect that. but, the underlying position has remained the same.
https://www.youtube.com/watch?v=PIYFUlR-Qy0