Ok well one if my really close friends I have known sice kindergarten has recently turned on me to hang with the popular kids. Recently we have been talking but mybfriends say not to be her friend but I want to. What should I do.

Do what you want to. But be careful. That's fine if you want to be friends with her still. But I wouldn't count on things going back to the way they used to. She'll probably still be friends with all of her newer friends too. And that's OK, just realize that she may have gone from best friend status to just good ol' friend to chat with every now and then status. Or who knows, maybe she's realized being popular isn't really all that and it's more important to have one very good friend.

I had the same experience at school, my ONLY friend in high school completely ditched me to go hang out with the popular kids... she left me to sit in the library on my own evey lunch time for a about a week... then she decided that she wanted to hang out with me again once the 'popular kids' stopped inviting her to hang out with them.

Like an idiot I let her back in only for her to do it again and again and again every time she had the chance...
She knew I would let her back so she had no reason not to do it.

My advice... throw her away and find yourself some new friends.
Yeah sure it might be fun for a week or so but it will only happen again, she is obviously not a very good friend to you.