Ugggggggggggggg this girl bothers me!!!!?

okay well theres this girl...... lets call her a. me and my friends hang out with this girl e who i have been hanging out with for like 3 years now. well this girl a shows up out of no were sometimes and steals her away from us. my friends are getting kinda annoyed to. i tried talking to her today but then shes like i can be friends with who ever i want to be with. one day we were going up to lunch ( im a young teen btw) and my friend gave e a hug and then a came out of no were ( like usually) and gave her a hug to. then my friend put her arm around her and said shes mine kiddingly and then she backed off for like 10 seconds and came back annoyed and put her arm around her to and went in es face and said shes mine right e and she just said yes because there "wifeys" ( long story) but then we got to my friends looker and e gave her a hug and the a said now shes mine! and gave her a hug then. then we got to es locker and gave her like 3. this girl is really starting to annoy us and we dont no what to do please help!!!!!!!!!