What is the ruling on delaying making up missed fasts for many years due to illness for a wife, and is expiation due from her? And how can one deal with her refusal to pray due to her illness?

The wife must make up the days she missed from Ramadan whenever she is able, because she delayed making them up due to an excuse, so no fidyah (expiation) is incumbent upon her. The husband must enjoin his wife to pray and explain to her the seriousness of abandoning it, and that it is not waived for anyone as long as their intellect is sound, and that obedience to Allah Almighty is one of the greatest means of attracting good.