Grow up ?!

Well , yesterday an older friend of mine was telling me how immature me and my friends are , and she was like "you guys , are like high-school kids, and sometimes elementary kids", I was like , so what?!, and she was like it gets annoying , and you need to mature , I told her in what ways do we act like kids , and she's like , the backstabbing , the making fun of each other , the meaness , the bullying . I told her , and why does it bother you , she was like "If you want to be my friend , I would like you to grow up and act like an adult " , I told her , you do the same thing !