1) Caffeine (I have one espresso in the morning, that's my personal limit)
2) Carbs (starches+non-glutenous grains)
3) Sugar (in the form of honey, fruit, and cane sugar)
I really didn't like the idea at first of adding those things back to my diet, but I honestly feel much better with them, and even that small rise in BP really makes a big difference in the fatigue, as I mentioned. Those days when my BP was 90/60 or lower were really awful, and if I'm glad to eat white rice and sugar everyday if it keeps me functional.
Other than prescription medication (which I'm personally distrusting of in general), it seems there is not much else to do to raise BP.
I've also found that walking seems to make improvements in my fatigue, also. On the worst low BP days, I wasn't capable of walking, I felt too exhausted and weak. Once I got it back up to 105/65, I was able to walk, and I noticed that the circulation/blood flow improvement seemed to be energizing and long lasting. I know you said your wife is too weak to walk right now, but if she's able to get her BP a little higher, maybe there is something like gentle yoga or some water aerobics that could work for her.