Heaven Help Me MY BEST FRIEND THINKS SHE IS A VAMPIRE! And it's really starting to creep me out...?

Well first that sounds like an obsesion, and she really needs some help on that, like a therapist. Two you could trick her into eating garlic pizza or having somthing near without her knowing, then say to your mom shes not a vamp, or take her pic, or put her in front of a mirrior. Remember knowledge is key, but how you use it is power. Read up on vamps, see how you could put that aginst her, and even if she seems wacked or your too good for her, your not (so to speak), your her equal, her friend. But last it could just be a phase, yes a long phase but just give it time. Hope this info helps, oh and it sounds like you got a pretty nice fashion sense.