Here is what u do bro.
If your GF has her friends call u, Im assuming she is doing it to see if u will cheat on her right or they try to get u to come back to her.
If your GF is immature, that means it would be easy to run head games on her and get her completely under control.
U gotta approach a relationship like this like a war.
She is obviously insane over you if she is so insecure she'd have her friends call u.
Use that to your advantage.
U can pretty much make a slave out of a chick like this and have her on your nut till the end of the world.
I have a friend like this who had 3 GF's at one time, and they all three were so immature and stupid they never found out about one another and they gave him cash, bought him shit and was at his beckon call.
So if u get tired of her being immature, retaliate and make her pay for being so insecure.
U could do like Blue Cut and fuck her friends but I dont recommend about.
Or do like SLLC and Kujjo and start hitting on her brother. that also isnt highly recommended.
If u want her to just go away, u just have to cut all contact.
A girl like this though would be easy to turn into a slave.