The person's hair is shorter in those pics than Sienna's hair in the ones from walking the dogs on the 12th and out in London on the 20th. I know that's not a solid argument, but I can't say for sure if it's her either. Anyone could have a gold chain like that, wasn't there just a magazine article where some other celeb had the same chain, why couldn't anyone else have it.
If it is her, I don't see how that's "out of control", I bounce around like that if the music's good enough, big deal? And why is it a crime to have a few drinks at a party, it's not like she's under-age? There are plenty of other celebs who behave a lot worse, for that matter. Being a celebrity shouldn't mean you're not allowed to have any fun at all ever. That last picture is just a split second in time, I doubt she was wandering around with that look on her face all night, pictures may be worth 1000 words but nobody ever said all of those words are necessarily true 100% of the time.