Face burnt by Spike. No scars at all.

Paper taps face. Badass Scar.

If I've got my limited knowledge of Greek mythology right, Tartarus was sort of a sub-domain of hades, so it wasn't hell in and of itself.

As for the pic, she didn't even get the scar from going there, that was just a paper cut from Spike belching up the 'Lost dog' poster.