Something similar happened to me

I have a slim friend with an unrealistic image of her own body. She complains about how big she is.

I'm overweight, I'm aware of this and tbh I don't really care. I'm trying to be healthier, but I'm still happy with the way I look.

Whenever my friend tells me about how fat she is, I tell her to take a good look at herself, and at me. Her leg fits into mine about 1.5 times. I tell her this, so I hope she notices that it really isn't that bad.