Where? I don't see any ass.
That girl probably has on heels and is arching her back as hard as she can. Not to mention that she has on those panties that give the illusion of making an ass look better and bigger that it acually is.
Anyway, while that is a sexy picture, you are out of your mind if you think that is Vida Guerra. She's not even close.
If you can see past such an amazing ass, you'll see no tatoo.
http://images.plus613.com/2400/vida-guerra-skins-01.jpg