I'm new to this group, hope my comments are helpful. Me stage 4 diagnos last july with tumors spread to liver, adrenals and lungs. I suffered wicked late onset diarrhea as well but I think I am finally getting the hang of it.
On chemo day I take 8 mg of dexamethazone and 8mg of zophran. At night I take 4mg of each then usually 4mg of zophran twice a day.
Key for my energy level is hydration, so I have a standing order for saline drip anytime I want it and use it often.
Plus I immediately change my diet to basically white: toast, yogurt, rice, cheese.
I was wiped out, had severe muscle wasting and couldn't walk, and probably felt like your wife is feeling now.
Now I'm driving, walking and have friends over for meals.