How can I get her to stop?

Ok so my friend is big. People call her precious and fat and crap and me and my other friends always stick up for her. But she is not the only victim , we are too because she is loud and calls other people fat *** , and that they look like ompaloompas. She even told two of our friends that they look like they were getting pregnant... wtf !!! She even calls me tubby ! I am gonna tell you now I am not the best looking girl in the world i'm a bit chubby , but I work out and run around the track. Anyway how can I politely tell her to stop this nonsense. I don't want to just blurt out that she sounds so stupid because that's rude. So can you give me a nice way to tell her to stop ?