Friend Help? Please???????? 10 points?

I have a friend named diana. Diana and i have been best friends since the beggining of the school year. Thusday (at p.e) when playing tetherball with me diana said that jackie was talking behind her back and she was also talking about me. she said she cant be friends anymore because when she plays with me she leaves other friends out. but yesterday (Friday June 3rd) When at music, Diana and I were playing music together and we were back on the track as best friends but jakie didnt like this at all she would say go away to me and she would also say that i took diana away from her which i didnt. jakie has always disliked me . Thursday after p,e Diana and jakie were away fom eachother and I felt bad because i think i was the cause i finally couldnt stand it but i didnt do anything. what should diana do? what should I do?