I don't know what to do about my best friend.. this will be a lil long..?

Ok, so heres the thing. My best friend is 1 year older than me and next year she will go to a bigger school while i go to a different school but we arent moving and we should see each other regularly. We just became best friends this year and heres why: last year her and well lets call her amy were best friends. so amy went out with.. ( lets call my best friend pat ) pats cousin. amy started to push pat away and focus on pats cousin. so then pat became mad at her and pat and i became closer and started hanging out more. then eventually we started to hate amy and we became best friends. all was good but then she started hanging out with amy again and i asked her if she liked amy and shes like no and then a few months later amy and pats cousin broke up and then pats cousin started to defend her in the halls and even defended her from me! she knows that my worst of all fear is her going back to amy after all we've been through and not caring about me and she promised me that that wouldnt happen. then a few weeks ago that stopped and i was like what you defending her is now over? and she said yeah shes a slut and i was like ok lol and then all was good. but now i have a baseball tourniment this weekend and amy didnt have a ride so pat said she ride with them and i was already coming with pat because i didnt have a ride. she just IMed me and said: amy is coming with us on the way because she doesnt have a ride and mom said yes but shes not staying with us. i said omg do you realize how much i dislike her and why cant she go with someone else?! and shes like if your going to have that attitude just dont come because i want to have fun and i said yeah well whatever i want to have fun too and we went back and forth and eventually i said well i dont want to fight and i want to have a good time and i will even if amy is there and shes like fine you can come but dont get pissed off just because you might be the third wheel ( she knows right where to hit and i thought to myself, you say you hate her then you go and hang out with her and leave me your " best friend " as a third wheel to her? ) and i said wow thanks. and shes like im just saying when there is three there is always someone left out and dont come crying to me that your that one. OH DID I FORGET TO MENTION THAT AMY WENT TO PATS TODAY ( TUESDAY ) AND IS STAYING TIL FRIDAY AND THEN COMING TO PICK ME UP WITH THEM? yes well during this little fight i have no doubt amy and pat were sitting there talking about me and in on this together the whole time. pat is my most best friend in the whole world and ive never had such a good friend and then when i think about losing her i ache so bad and when i tell her that she just says you sound so desperate its kinda weird.. and i feel retarded and i have other friends.. good friends and she just says remember you dont own me and it sounds like she doesnt even care about me and whenever i try to talk about something like that she gets mad and is like im so sick of tired of your whining and complaining about amy!! someone please help i dont want to lose her as a best friend ESPECIALLY to amy!! i honestly dont have a problem with anyone else she has other good friends too but its just amy..