Really? A girl so much as mentions a past event with Jill and everyone assumes it's sexual? You all have dirty minds.
I didn't get a sexual vibe from that particular incident. As I've said before, Jill's pronounced insecurity about sex is hard to square with her fooling around with her BFFs. I thought it was one of the few (only?) times when Jill caught her parent's ire the same way Lana did, and she doesn't like remembering it.
We know the Royces take appearances very seriously and put a lot of expectations on Jill; that's why it was important for Bianca to help her loosen up at times. But it stands to reason that getting caught drinking stolen booze might be more than a casual grounding, too.