I'm just finishing up the latest book in George R. R. Martin's fantasy series, A Song of Ice and Fire, and this roleplay has been wriggling around in the back of my head since the second book.
The basic idea is this: A young lady is betrothed to a young lordling. It's a good match, favorable for both their houses. The problem is, this young lady doesn't want to marry. In fact, this lady doesn't even like the company of men, not that her opinion means much. During their wedding feast, dancers from across the Narrow Sea perform for them. The young bride is smitten with one of them, and they start seeing each other secretly.
(Or alternatively, the lady meets a whore somehow and sneaks off to a brothel to see her.)
I don't want to use canon characters for this, but creating OCs within the already-established houses is all right with me. Mostly I'm looking for the medieval lesbian romance, Westeros is just a nice backdrop for it. The setting doesn't have to be strictly Westeros either. We can make up our own fantasy world if you'd like! I'm certainly down for a more magical setting if you are.
This plot can be as kinky or as vanilla as you're comfortable with. I do like the notion of the dancer/whore being much more experienced than the lady, and I'm willing to play either side of it.