Unbelievable! When I first looked at some of the pictures, I thought that it was chalk, and would wash off....nope, not according to the articles. She's using acrylic paints!
Sand paper would be to easy for her....I'd rather see her try and scrub it off bare handed....wear some skin off!
I've spend time as a Boy Scout Leader, and we teach the boys that they should appreciate the places they go, and leave them in better shape than they were when they arrived. We always bring some trash bags with us, and would end up carrying out other people's trash.
We leave with what we brought in, with memories, and photographs of wonderful times. We don't leave anything, except maybe some footprints, and try to avoid that!
Painting these wonderful places is insane, and I that they catch her, and make an example of her!