Sucks for the girl, but legally there's really no other way unless she can be pardoned for some reason (e.g. because it's a minor crime). Legally, I imagine this isn't any different to carrying a gun and using it for defense. She may be charged using a different law, but that's it.
Now whether pepper sprays should be illegal... At first I'd imagine they shouldn't, but I'm not going to say more because I don't really know enough about them (and specifically how dangerous exactly they can be).







