1. Dont know by you, but I read GL to see girlsxgirls, not girlsxboys.One, I could be wrong so there's still a chance she's your idea of a pure yuri maiden. Two, If that's what's got you in shambles, you should've left as soon as you found out the FL was actually dating a man in the first place.
2. Just cause she dated a guy didnt mean she had sex with him, so gave it a chance, but looks like she did, so guess its time to drop it.