Need help with friends? I might leave the group?

I became really good friends with this girl named Natalie in school. She's really nice and we always hangout. Now the bad part is her two friends named Lexi & Erika. Their both really mean. When she introduced me to them at lunch, I offered them some chips and Erika grabbed some from out of the bag without even thanking me. I always share food with her but she never shares her. Natalie admits to me when we're not hanging out with them that they can be very mean. Their nice at times but rarely nice to me. Whenever we're all walking together they'll push me at the end so they'll be in the middle. I have been ignoring it, letting them have their way but I'm annoyed. Lexi is always using me as the one to make fun of, and give bad comments. I don't understand how Natalie ended up with these jerks. On friday I told them I'm getting tired of this group, and that their really mean. I told them the only reason I ever hung out with them is because of Natalie. I told Natalie I kind of want to start hanging out with my old friends. I used to be popular and hangout with popular kids. Now I'm hanging out with these losers (except Natalie she's not a loser) & I don't even enjoy it. I loved my old friends and they will always except me in their group again. Should I just hangout with them again? I want Natalie to leave them because they don't belong being friends with us. I might sound mean but they are terribly mean. They deserve no friends. They can laugh by themselves and their stupid jokes. Their always making fun of fat kids when their not so skinny themselves. Their always saying I'm too skinny. Fck them. What do I do? I wanna leave but I don't want to leave Natalie.