a) Tell her she'll make a scene and embarrass herself.
b) Don't be her friend.-Ditch her or find her a new friend (Very bad idea unless you strongly dislike the person)
c) If they accidentally hurt you make a scene. (Meaning cry, shout, or fall to the ground) That may make them more careful.
d) Annoy them as much as they annoy you until you can make them see how you feel / If they tell then tell the teacher they've used you and tormented you since you became *friends*.
For my crazy friend, options a, c, and then d worked until she found a new friend- option b- (I found her the new friend)