I think that 99.9% of ferrets would ignore the wheel or just use it as a sleep spot. She can try using a wheel, but you'll have to find a
huge one seeing as even the largest Wodent Wheel is pretty big, and it'd have to be about double (or even triple) the size for a ferret.
For a cage, especially since you mentioned he doesn't get a lot of out time, I'd suggest a larger one, such as the F-475 by Martin's Cages, one of the two biggest SuperPet cages. or possibly the Ferret Nation cage. And although a second ferret would more than likely keep him good company, when she's already not giving the first one enough out-time, I don't think it'd be good to throw another into the mix

Have you tried talking to her about how important it is to give her ferret playtime outside it's cage everyday? Ferrets are very, VERY playful and extremely energetic. Keeping one cooped up in a cage is practically cruel. A ferret needs around 8-10+ hours of out-time daily. Maybe ferrets aren't the right pet for her?