[Rant] A weird situation from school today. I want to know if I'm in the wrong.

So it all started in first period today. I don't remember how we got on the subject but we ended up talking about LGBT people we know at school. The girl I was talking to said, "I used to be gay." Those were her exact words. "I USED to be gay." I said, "You can't just stop being gay. Either you were, and still are gay, or you aren't and never were gay." She says that she used to be gay because she dated a girl once.

At this point, I realize what she's referring to. Around the time we first met, she told me a story about how she thought that she might be gay, so she dated a girl, but then realized that she was definitely straight.

After realizing this I say that she might've been curious, but she wasn't gay.

It goes back and forth like this for a little while until the person sitting behind me chimes in and says that my friend is right.

Now I'm one to believe that if everyone else is wrong, it might be you that's wrong, so I give up. I came here today to ask, who was in the right? I felt certain that I was correct, but I seemed to be the only one to think that. Who was right in this situation? Sorry for the long rant/question, but I had to know. Thank you all so much.