She should've never been against gay marriage in the first place.
It's not something where you start off thinking "GMOs are bad!" which might be a typical initial reaction to "unnatural" foods before you do some research and realize GMOs aren't the devil.
Having a thought that gay people should be second-class citizens and holding that thought for the majority of your life is not a "oh I got educated" or "my opinion evolved!" kind of thing, in my opinion. Especially not at that point in her life. The typical response is "well she totally was in favor of gay marriage but she had to lie about it!" which honestly doesn't make me feel any better about it.
Or, somebody can have a change of opinion. She grew up in an age when gay marriage wasn't socially acceptable, and as much as you want your politicians to be ideological purists, it's a simply reality that the environment that you live in has a
strong psychological impact on you. It's a very normal thing in the human experience to form your opinions on topics based on the opinions of other people around you.
Just like Barack Obama, Bill Clinton, Harry Reid, Joe Biden, Chuck Schumer, and yes even golden boy Bernie Sanders, virtually every politician has had an evolved position on gay marriage. Why? Because huge percentages of the American population have had evolved positions on gay marriage, not just racist, anti-gay bigots, but progressive, fair minded people who were products of their age. It would be nice to say, "I wish I had always had the reasonable position that I have today on Gay marriage and LGBTQ rights," but most of us -- especially those who are older who grew up in a much different world -- have not. SO you can choose to disqualify virtually every Democrat and most reasonable people from office, or you can choose that normal, fair minded people can hold opinions that are wrong at some point in their life, and then change their mind on them later.
Me, personally, back in the 1990s, I was luke warm to gay marriage... And not for any good reason, I think it was a mix of childhood bias and my immature teenage argumentative nature to be against everything and think everything was stupid. My state was the first to legalize it, and I took up the argument (personally) -- at the time -- that it should be brought to a ballot initiative vote instead of being decided by judges. I have gay people in my family who were some of the first people in the country to be married, but I still held this opinion myself. Within a few months of that judicial opinion, and seeing the quantitative life improvement that it was making for gay people in my state, I changed my mind. In retrospect, my private opposition to gay marriage and how it became law was stupid, misinformed, selfish, and short-sighted. But for now about half of my life, I've been a strong supporter of gay marriage. Is my opinion on gay marriage today disqualified because when I was 17 or 18 I was stupidly opposed to it? If we have an identical position today, is your position
more right than mine because you've had that position your entire life (theoretically), while I've only had mine for 15 years?