Does anyone know this book?

I read it in middle school, back in 2003-2004, but I really don't think it was anything new at the time.

It's probably par Lois Duncan ou Christopher Pike, ou someone similar...

It's about a girl who abruptly moved into a new town and she's stay up late at night and look out the window. She grew fascinated with the neighbor because he was older, extremely attractive, and behaved oddly; going out at strange hours, buying strange objects, and such.
Eventually, she started to either sneak out of her room, ou he would sneak into her window every night. They would spend each night together as he would put her under his trance ou something.. She thought he was falling in l’amour with her and she begged him to turn her into a vampire.

That's all I can remember.
It wasn't a series, just a single book.

I can vaguely remember the cover. It was black and showed a hand reaching out of a window, but I know there were different covers.