So a friend if mine keeps saying she's fat. I don't know what to tell her, I mean she is not really over weight but she does have a little tummy, her stomach dosent stick out (she's good at hiding it), no muffin top none of that. She's just normal? I'm not sure, I've just been telling her. "Ashley you look fine."

I don't feel like in being a good friend by just telling her that.
What should I do?:(

She is insecure. I don't know why though.

thank you for your advice.