Looking closer, I think she has vitiligo, a skin condition that causes light and dark patches to appear. Her face, hands and feet aren't too bad, but around her pelvis, its so stark it looks like tan lines. The tats are probably her way of dealing with it. She really is quite beautiful.

I've seen her on R/ you are dec correct about the vitiligo, but I think the tats are to cover a C-section scar.