Hermione treated the situation the same way she had whenever she'd pulled away from Viktor. Reaching up, she brushed Ginny's cheek with the back of her hand to show that it was something within her and not necessarily something Ginny did.
"I know you're in here all the time," she gave a small smile and added, "but there's usually giggling not moaning coming from behind the curtains." True enough they could cast a silencing charm but that would look even more suspicious once Ginny emerged to return to her own bed for the night. Unless of course, she wanted to stay and leave in the morning. It would be easy enough get her out past the others since tomorrow wasn't a school day.
"That's entirely up to you," she added then searched Ginny's face while she awaited the decision.