text: whats the best way to tell a girl that shes not fat when she says she is?   that's tough. it's really hard to change her thinking about being fat, but you can help build her self esteem. have her look at herself in the mirrior, and name all the things she likes about herself, and then point out some things that you like about her. that should help her feel better about herself and make her look at herself in a more positive way.