Try showing her something scientific, like an article perhaps, that PROVES being overweight is unhealthy. Science articles convince people so easily, but that's becasue they're also mostly true. Try searching on the net for articles and stuff. But maybe I'm only suggesting this becasue I like science. I'm not sure. But I think it really would help, but you might want to convince her in other ways that other people might post...Good luck. ^_^