The Maff zone is a proxy for the intensity of maximum fat burning. Maffetone actual says this somewhere. Any chance you could get a Metabolic efficiency test done on her to see what heart rate it occurs at. If so make sure there is good cooling when she does it… I didn’t when I did mine and I suspect it affected the results.
Hmmmm… I wonder, with her RN connections, if just such a test as you suggest is available to her. I shall inquire Thanks!!