My friend is angry at me for unknown reason,help!?

so i figured out my friend is mad at me for an unknown reason,she has yet to tell me that she is mad at me but im sure she is since she hasnt contacted me after ive text her and wrote to her on facebbook,so im gng to email her,but i dnt knw what to say..this is what has been gng on,so my friends all been hanging out but they never invited me to any occasion,i find it odd cuz we all been trying to hang out together like we use to,and also it weird cuz my friend has visited me this past month and we had fun together all of a sudden she isnt talkin to me and has put mean comments on her FB,which im sure was towrd to me...im not mad at my friend for not invited me to any of there get togethers im just bummed they didnt tellme..and i want to know why they havent invited me and why they arent speakin to me..i havent said anything bad about them..im the nice one of the group..lol..pleasedont think im jealous that they r all hanging out,im glad cuz my friends stop speakin to each other and finally they r getting along....idk what should i say to my friend