I think it is EXTREMELY unlikely that your marital problems have anything to do with your DD's expressed sexual preference. As far as I know, there is NO decent evidence to suggest that marital problems have such effects on children.
Try to be respectful of your daughter and avoid questioning whether something so intimate and personal is an authentic part of her. It is certainly nothing for you to externalize for her and blame on someone else. It won't help her. It will hurt her.
The idea that femininity and liking princesses demonstrates one's sexual preference is also just plain wrong. Plenty of lesbians and bisexual women are very feminine.
I'd like to suggest that maybe you "KNOW" your daughter less well than you think. We all thought we "KNEW" the WAS before the WAS walked.
Start with a beginner's mind. Listen to your DD. Believe her. Be happy that she shared this with you. Sexual preference is simply a property she has, like hair color or eye color. Given you don't plan to date your own daughter, her sex like should not be any of your business really, or affect your relationship with her in any way.
I work with college students all the time. Your attitude WILL hurt her. Listen to her and trust. Don't judge.
