Context - LTR is young, fresh out of high-school young. I'm in my late 20's. I vetted this chick for a long time, and this is a situation that has been occurring long before we were official.

She still does "sleep overs" and specifically with one of her friends who is a gay guy. The dude is chill, I'm cool with him. However, lately the idea of her sleeping there is turning me off. I withdrew some attention after the last time she stayed there, but feel like I need to bring this up ASAP before I resent her for it.

Opinions on how to bring it up without having a long conversation/argument? Just flat out say it's turning me off & see if we can compromise? The LTR has been nothing but happiness, seems I'm the one always coming up with an issue/a reason to be "disappointed" I think this one is fair.