Please Help What should I do?

Hi I'm Karen,okay so here's the story in the 10th grade me and my best friend named Lisa met but she already had a best friend named Helen that was at another school so around december we had met and started talking and became cool and after that we all called each other best friends and started hanging out with each other and tell each other everything you know the typical stuff best friends do so this year was our senior year and everything started to go crazy we all had boyfriends but lisa had broken up with her boyfriend and was talking back to her ex bt still talking to her bf she had jus broken up with and he found out that they had did something and she told us about it and i told her she should have never been talking to her ex because she had something good even though they wasnt talking at the moment bt she had told helen and helen texted her back and told her "you always ******* up something good you cant never do she right" when lisa told me that i felt that helen didnt have to tell her like that she could have been a best friend and been there for her so they got into a huge argument and helen told lisa f her and dont worry about her no more so a few weeks went bye and lisa tried to talk to helen and helen still had an attitude now while they were going through this i was still talking to both of them bt helen was acking a lil funny with me from time to time bt all of a sudden helen stop answering my calls and text's and her and lisa got into it again because lisa told her that they argument had nothing to do with me and helen was trying to fight lisa so after that they never talked again until one day helen was going through something with her family about graduation so i talked to her then lisa called to c if she was okay then they started talking again all of a sudden helen started acking funny with me again like if i needed to talk to her about something she always tell me she with her boyfriend she cant talk to me so i just left it alone but me and lisa are still best friends nothing has changed between us but i havent talk to helen in like a month and since her and lisa started talking again i feel like since her and lisa are cool again she doesnt talk to me and she acks funny now she has a boyfriend i understand that she wants to spend time with him cause i have one to, but people are telling me that im wrong for not talking to her but i dont think so ,so what should i do