It is not like she tries to be healthier. If I knew vegan diet doesn't work for me, I wouldn't force it. I would also cut out drinking - I seriously don't see the appeal in chugging gin and tonic every night. All she does, at least of what we saw and heard, is taking medicine. Thyroid gland can be really tricky to handle, but adequate diet and lifestyle are a huge part of it.
That is exactly what you say, she is so used getting everything she wants, how she wants it, when, where, that she just won't listen.