I really want to join mma...?

im a 15 year old girl and im in really good shape. i work out A LOT, and run even more so. I want to push myself and get into mma. ive always lke wrestling and stuff with my friends. so i think would enjoy it. Theres only one problem. my dad thinks its way too dangerous and i will become a vegetable from being hit in the head. i also was thinking about fighting when im 18 for fun and amateur, and just train and only use it for self defense. i need some evidence to provve to my dad. help? PLEASE???? :(