I spat on a landwhale's face and almost slapped her
Did she start it?
She offended me by being ridiculous. I left after that.
You shouldn't resort to such gross tactics just because you're offended. Walking off and ignoring them is the most rational choice.
I want to teach her a lesson that she shouldn't be disrespectful about somebody's appearance.
I see your point but maybe there is another way to express your feelings about somebody's behavior without being physically disrespectful to them.