I think I'm going to tell my best friend she's reached an unhealthy weight.
Do you really think it's a good idea to comment on her weight?
She never stops eating and it's getting dangerous.
I know that you're trying to help. But unless she's expressed discomfort with her weight, it's rude to tell a friend they should lose weight.
I have to help her be the best she can be.
I understand that you want to help her, but I don't think telling her that she's gained weight is going to do that. I'm sure she's aware of that fact, and will only feel uncomfortable if you comment on it.