What do i do??????????

so i will be seeing my cousin soon and i do not like them at all!!!! they judge me (which i don't care about cuz everyone does) they r annoying, the take my stuff, and they have to go agents everything i say! she has no tact when she says it too! like one time she told my cousin that he was ganna grow up fat and die of diabetes! shes soo mean and if i say anything she tells her mom and dad and im suddenly the bad guy! help!