I understand where she's comin from, when I was young I used to think it's better to just be straight as well (I'm bi-romantic). It's easier, and you won't get into any trouble with your family. She's not coming from a malicious side, but she ended up taking the wrong decision. She should've just communicated her uncertainties and worry since the beginning, and accepted he's answer after the got it.










Her reasoning is too weak. I think the only reason I can imagine that would make an impact / justifiable, is if she's gay or a friend she's close to is gay, then they got bullied or betrayed for being gay and she sees this. So she got scared for or main characters.
*For our maim characters