You are right she probably wasn't a virgin. There is one victim that went public a few weeks ago on CBS, (I think) that described her discomfort during grooming and eventual rape that took her virginity, if that is what you are thinking to be the heinous aspect... not sure.
The grooming or easing these girls into this shit is a component that likely takes on all different forms and key...
Let's place you in this scenario of yours, you are between 13-17 & had sex a few times and you are taken to a party that was built up so you were excited!! You get there and it is full of old women or old gay dudes that pass you around as a sex toy...
Is it somehow less heinous because you aren't a virgin or have extensive sex experience for your age? No, not for me anyway, I wouldn't want that shit now and Im pro tier sex god, old women are still gross and I still want to destroy globohomo.
I'm not excusing anything about Epstein, but my feeling is that these girls weren't rookies, as bad as that sounds.
I find it to be improbable that it would be at one of these parties, that she was deflowered.