what do i do if there is a girl who constantly annoys me and wants to talk to me alot. when im not intrested?

A girl can just be interested in what you know about certain topics, not necessarily must be boy girl interest.

I'm with J on this one. Simply saying, "I'm not interested is ok".

Judt listen but make minimal response: she will get the message

Tell her directly your not interested. If you want to be nice and she wants to talk and ask why, let her, explain and it will at least give her closure. She probably worries, but hopes she's not annoying you, if you tell her directly she will likely stop, shel also probably feel like it's her fault your not interested because she annoyed you, so if you want to be really nice you could explain that, you never were interested and it wouldn't make a difference what she did, if that's the case. Just be honest and talk, and then if she continues block her on everything I guess.

You could try be friends ?

flat out let her know you aren't interested.

Depends on how douchey you want to be.