How can I make her stop? It's so annoying?

My friend thinks she's fat, but she's not at all. She's skinny.
She's smaller than me also, by quite a lot, and she thinks shes fat and it hurts
me when she calls herself fat, and a "bubble" because, if she thinks she fat, i
must be ENORMOUS to her, and it really hurts me.. I tell her she's not fat and
she says she is and goes on, she tells me shes at the gym toning her theighs cuz
shes so fat..and i HATE it.. I asked her why she's so obsessed with being a
stick if no one cares about her figure, which is pretty much true, and she says,
im not doing it for other people, im doing it for me. i dont feel skinny, i need
to be thin. i can go ahead and be a "stick" if thats what it takes to not be
another example of America's obesity" what can i tell her.. how can me and my
friends get her to stop because its really hurtful to us, and we dont understand
it.. she barely eats to and we tell her to but she just says i cant... help
please!
show her youtube videos of peoples anorexia stories