Hummmm ....
I think it's a fake, with no doubt. Yeah, yeah, yeah !!!, with no doubt!
The main problem is "money".
With money, the magazine owner makes any thing. But I'm sure that Kristin would not sell herself for no money. This kind of scene is not part of her shape. In all Kristin interviews, yes, in all the interviews of her, without exception, the interviewer always asks if Kristin would make a naked scene and Kristin always answers: "NO".
So ... I think this is going to be the same case.