This is allegedly a nude of Scout Willis naked in a bathtub
There is no head shot, but the mole and tattoo detectives seem convinced. (Read down the thread.) There is no indication of where the picture came from. Is it a leak? If so, why are there no others?
Based on my motto of "remain hopeful but skeptical" (доверяй, но проверяй), I think this probably is she. Compare to this one and this one.
And we know she's not shy.