First, I’m sorry she (and you) have had to deal with cancer cause cancer is horrific.
In my own experience of being treated for cancer there was a team of doctors & each has their speciality. I don’t expect a specialist to speak with me about diet when they are specialized to treat cancer. That is the job of the “family doctor” or physician in my mind.
Are you from another country where healthcare has a more holistic approach? Believe me, I agree that the US healthcare has issues. 💜