I have a ex bestfriend and i want to become friends again but people tell me i shouldnt what should i do?HELP?

i have this best friend who's not really my best friend anymore we just randomly stopped talking for some reason and i really want her back i miss her i miss texting with her and going to the mall or movies with her or going to her house but everybody tells me no she wasn't thee right friend for me i felt like she was but i guess she wasn't but another reason i stopped talking to her was because we would always be together just us and to everyone we would be knowed as thee "unseperate sisters" but my bbest friendhad this other lil friend that i really hated and she would hang out with us more often and even more that that little *****(sorry for my language)stole my bbest friend and my best friend actually kinda ignored me and picked her(well that's what i felt)but even though my best friend would say she would rather pick me(and in that week that we got in a fight there was gonna bee a field trip we were gonna go to corpus christi and we had to pick partners to go with and she actually picked me instead of her)so i kinda think-ed too stop talking to her but i felt bad cuz we had so much memories i met her in 6th and now that were in 7th i cant believe were gonna stop being best friends so i stopped talking to her and texting her and she saw that i ignored her she even told me why aren't you talking to me but i ignored her like she would ignore me with her lil friend so that week we went on our field trip and shee went with her lil friend and i just went with this girl who's just my friend but i was kinda bored with her i think being with my ex best friend would of been better too go with so HELP!should i forgive her of not?everyone tells mee if i do its the biggest mistake of my life but i feel like if i need heer i felt like i was happier with my old bestfriend cuz now i dont have a bestfriend im kinda a loner but i still have my friends but i feel like if i dont fit in with them HELP!.....someone! pleasee!:(