With the scratches that Jeff pointed out under her chin I doubt this coin would straight grade. Those marks were deliberately made. I think PCGS got it right. You should leave as is.
If it was graffiti, wouldn't it spell something or form some kind of pattern? I thought that was the line between bag marks (random / non-patterned) & graffiti.
Graffiti consists of words or drawings. Since this looks like a tic-tax-toe box it's considered graffiti. It was deliberately put there as is all graffiti.
Graffiti: "writing or drawings scribbled, scratched, or sprayed illicitly on a wall or other surface in a public place:" So PCGS believed the scratches were put there deliberately so labeled it graffiti.