How to get my best friend back?

It’s obviosly “Best Friend Forever and Ever”. ‘She’ gave that name for us. She’s actually my BFFnE since 1st grade and we always get in the same class. But when we seperate(different class) she changes. She changes a little flirtatios, more..umm… the thing is she changes a lot! We usually just hang out together but now, she had join a gang, a gang that I don’t like. It’s not a gang, the gang, was to make fun of boys by bullying them. And the from the 1st month til’ the 5th month, break time we usually came out to see each other. But now, when I came out, go to her class, she was not there, she was with her gang buying some food and chat a while in the canteen. It hurts me a lot, even now I’m typing it now, I want to cry but I can handle it. That’s just the start, she only came to chat and have fun with me only if my mother send me some foods in break 2. She always in the badmood if I’m following her when it’s pray time, then okay, I’ll just pray behind her(I’m moslem, so I need to sholat together in the school), everytime I was always looking at her, she was having fun with her gang. And everytime I remember something bad or good about something I miss, it hurts me 9.999.999.999.999.999.999.999.999 times a lot, so I felt that I want to cry. I wanted to tell her about it, but I can’t… How? how to tell her? how to tell her that she changes? Please help…she’s the 1st person in my life that’s very important(parents no.2) !! pleeeassseee help…cries