Slander??? I want to choke her!!!!?

It sounds like she needs counseling. Perhaps she's looking for attention. Even negative attention is attention. If she has not brought charges against your father, then it could be slander. I would ume he's heard about this? If so, have you asked him what he has/is going to do about it? I don't think you should get yourself in trouble dealing with her as she is a minor. You might check with an attorney to see what rights your father has. Most importantly, you should discuss this with your father first. Good luck.