My cousin is really rude to me?

We're only 10 and we used to be best friends. We kinda still are but she's started being rude to me for quite some time now. She starts calling me things like butt holes and annoying little turds and says 'your annoying can you just go away' when I haven't said anything. Sometimes she blames me for things I haven't done like she says 'Stop being rude to me you little turd' or something like that, when shes the one calling me names. She says it so seriously not like laughter or any kind of joke after it. We do talk alot on the phone but she is still SO rude. Can someone help me?