When do girls/women stop being so mean?

I can't handle this girl anymore she was my best friend then i called it off because i couldn't handle her and her drama all the time. Now shes trying to get back into my life by talking **** ( i never retaliate, my boyfriend always tells me that karma will have its way with her). My boyfriend and hers are bestfriends and i want to make peace for them but shes to immature to answer my calls or call me back she can only text because shes a coward. Do i just give up? I really want to but at the same time i want to know that i tried to stop all the bs. Its really stupid considering were 22. Its like grow up already and get over it.