People can change preferences over the time. As we age our brain chemistry does change. I knew someone who dated women in her twenties, yet ended up marrying a man in her forties. It was confusing for her. She had been attracted to women her whole life, yet something changed as she got older.
Attraction is too complex to narrow down always to one or the other.
Even Elton John has said once in a while he has found a woman attractive and he is as gay as they come. It's not always a 100% for some people.
I've known people who were straight most of their life and then found themselves later in life drawn to their own gender. The brain is a strange thing.
It's even harder when people say you can't change. You aren't allowed to change. What you were attracted to in your youth is what you must stay attracted to for the rest of your life. That's not fair.
So I think it is possible what happened to this lady. I've read stories of this very thing happening. I knew someone it happened to. It's confusing for everyone. Attraction is just not static for some people. So maybe she was lesbian at that point in her life but as her hormones changed and her brain chemistry altered, so did her tastes. It happens to some.
There are a lot of sexualities, to call it preference is shallow. She wasn't a lesbian at some point. She probably just like women to that point, she discovers someone else she liked, other than women. She can be Bi, Pan/Omni(gender blind). The author disregarded it and treated the issue as some sort of sordid thing, a shame that must be hidden.
What exist are preconceptions and misconceptions. Everybody should be free to love whoever they want, discover and rediscover themselves as much as they want, although people insist on old conceptions of black and white in terms of sexuality, there's so much more to it!
You have no right to decide other people's sexualities for them. Heck, other people can't even figure out what they are sometimes. Some DO feel they are a lesbian, but then start to feel another. Just as some thought they were straight only to find at another point in their life they are more bi.
The author is writing the character as they see them. Perhaps this character really did believe herself to be a lesbian at that point in her life. It's so confusing.
I agree with your last paragraph but not your first. Good authors let the characters write themselves. The character may have seen herself as one way at that point in her life and gone around describing herself as lesbian. If that's how she saw herself, the writer would have to reflect that in the character. It's not the author pushing a narrative, but showing us the character as the character saw themselves.
Also perhaps the character regarded it as a shame and the author is trying to show the character's feelings. This doesn't mean it's the author's feelings. The author is trying to make us see the world through the character's eyes and if the character felt ashamed by it, then that would come through. The character is learning, growing, and finding herself.
It's not fair to assume that everything represents the author's opinion. Many authors write characters that are completely contradictory to their own beliefs or views. They want us to feel the character's emotions though.
Once again, preference is... What position you prefer, if you like bondage, if you like to cuddle in bed or not... If you like orgy or not... That was my point. About the disrespectfulness... May not be ignorance of the subject by the author, nevertheless, non accurate. There's no ex-gay, ex-lesbian, is not a disease! And for the record, this is not narrative, is science!
"understanding her past as a lesbian-" UM HELLO ARE WE BISEXUALS A JOKE TO YOU?? NO LESBIAN WOMEN WOULD DATE A GUY FOR FUCK'S SAKE