Maybe in the year 1400 she could 'return' to a natural diet, but at that point lard and veggies would be considered natural if you lived in europe.
Sometimes you have to prime the pump to get people out of a rut.
Anyway, diet is not the fix for everyone in every situation, which is why you see a lot of success stories on cz outside the Diet Forum s. And it's why you see a LOT of very healthy people who eat absolute crap food with impunity.
There is no 'surely' in health, otherwise there would be 1 forum on 1 website and everyone would have perfect success.
And though trying 5 or 6 things might sound complicated to you, I always have a plan for people when I give advice, even if they don't choose to follow through.
I don't see any real help from you here for the o.p., whereas at least I made some specific food suggestions.