I think my 'friend' is a cannibal?

Ok so she always says it, she loves the taste of blood-humans blood and shes just nuts! At first i thought it was a act but she bit my friend megan and went through her skin and swallowed it and said it was good. Shes bit me b4 too and done the same thing. Its gross and im scared. I try to ignore it but when she gets mad at me she likes to grab my arm and stick her nails into me. Sometimes she says i like ur skin and she licked me once- not aully but in a im-going-to-eat-you way. I have to be forced to be her friend bc when im not she gets over the top angry. Im really scared what do i do? :(