The Harem Girls (my name) made me think I might be seeing the top of Holly's dark patch. It's still not clear to me if I'm seeing bush, or seeing some dark underwear/costume or maybe it's only a shadow (doesn't seem to be a shadow).
I would be curious to hear other opinions on what we're seeing as Holly gyrates her hips.
The Harem Girls
Many thanks go to the original posters and cappers!