There's a not so subtle "Sluts deserve whatever happens to them." vibe I get from the argument that it's okay since she already showed 'em.
I just knew one of you would make that dumb ass comparison. If you notice, nobody said or even implied that.
The point is whether she was okay with it. And her actions before and after are consistent with being ok with it.
Because people often don't explicitly state things are ok to do we have to sometimes read into their actions.
For instance, do you explicitly ask for permission whenever you have sex? Of course not, most people probably don't. It's more like, you make a move and if you are told to stop you stop, but otherwise you do your thing.
The context here is that this sort of thing goes on pretty frequently at these types of events. It's not that you can assume that every girl there is cool with it, but if her actions are consistent with it then in context you can read into it.
She did it herself earlier, then made motion that suggested she wanted Elliott to do it. And that's without us even knowing anything that was said between them. It's pretty reasonable to conclude she was ok with it.
Like I said before, they weren't shopping at Walmart. The context is a big deal here.