I'm curious if you really know this woman or not. If you're on intimate terms with her and someone she trusts to confide in then your story about her doing nothing to get healthier is probably true.
I'm curious because of people I work with who think they know me. Some would say they know me well but only one person (at work) truly does.
We all tell ourselves stories to make things make sense. I'm just wondering if this is your story or her story.
Is she fat because she chooses to do nothing about her weight?
Does she struggle with a medical condition that you're unaware of?
Does she lack the tools to make changes in her life?
I would chat with her when I'm feeling particularly snarky, but I wouldn't ever call her on the phone.
"An error does not become truth by reason of multiplied propagation, nor does truth become error because nobody sees it." - Gandhi