Haha, that looks highly suspicious. Now, I'll say, my wife is quite juicy and she's sometimes produces panties nearly that coated in "fluids" after a night out (which I'm sure are the result of her being turned on, probably from being flirted with) but never quite that much staining or so white. I think, at the very least, it definitely is a result of her being very turned on from flirting / dancing with men but the splotches on the dress though... how did that happen lol? Unless she fingered herself at the hotel... with her clothes on? Not sure how that happens.
Why a hotel? Did they travel a long ways to go out? Seems odd...
I dunno man, I wouldn't say its 100% but it seems highly suspect.