For girls---How to make a girl not like you in a nice way?

Im 13 and this girl is obsessed with me. She texts me 24/7 and calls me to. She gave her friends my phone number and they beg me to ask her out. I have tried to tell her that I dont like her in nice ways like giving her hints but she just wont give up. I told her one day that I flat out dont like her at all and she STILL likes me! I dont know what to do to get her to hate me or never talk to me or just like someone else. P.s. Shes not ugly or anything I think shes kinda cute but Im just not that into her. I want to tell her i dont like her but in a nice way