That's not at all creepy, Hit. XD
Anyway! Ryooooooo. He will be made to suffer - not like the Slytherins, but because he's M's friend. She will draw on his face and make him look like a fool - continuously. She'll love him though.
She'll probably be intrigued because he's a vampire and will constantly tease him about being sparkly like Edward who I think M has a slightly obsessive crush on - though mostly because she wants to cut him up and see what's inside. Who says fandoms can't exist within fandoms! It's fanception! *flails* So friends. Yeah. Lol.
She'll put itching powder in his boxers if he follows her around. She doesn't like creepers and if he follows her then he will be elevated to creeper status and he will just be tortured...horribly. She'll just...set his hair on fire or something equally horrifying and amusing (to her). Yeah, she doesn't take too well to the weird ones. I'm sure she'd find him cute eventually. He'd get more than a few hexes if he's insists on stalking her though. Lol.
Yumi + Millie + Gunpowder = Oops? She'll be lumped with the other Slytherins -- fair game.