This type of girl is real, and I've encountered her lol. Real creepy and annoying, not even 1 minute have passed and she already sent more than 10 messages. If I did reply, she then quickly reply it with another 20. And we're not even going out.
Oh, she doesn't have suicidal tendency though. If you want to ask. There's another girl like that but she's an attention whore (which the whole class doesn't take seriously) basically.