Miss I know everything 😟

Guys i value friendship so much. 
Basically I have this friend who is so insecure about herself, coz she hasn't got a "nice" body. She's kinda chubby on her upper side (breaSt, belly and arms) with skinny legs. I push her to feel happy about her self. I recently asked her to join gym together ,she told me that she will eat and get "fat" anyway and she don't see the point of it. Sometimes she tends to take it out on me by discouraging me. I don't have a perfect shape but I'm just a slim girl that loves her body, and sometimes she tells me that "I'm lucky and that I can wear anything that I want".😣
She is so insecure that even if a guy looks at her direction , it's flirting, even if someone likes her picture she will talk about it for a whole week. If a guy text her "hello" she will brag herself about it. She always Always talk about herself. I tell her all the time that she's beautiful and she will find a good man but she thinks I say it for the sake of it.
What I don't understand is that we will have a good conversation on Monday and she will not talk to me on Tuesday for no reason. She never want to go out, she never want to get in my pictures. I guess what she wants is to have good conversations of phone but is that it?🤔 thats not friendship then👎🏾
Any ideas or advice?