I have DM. Have had it for about 17 years(undiagnosed until Sep of 2003)
As far as the fatigue is concerned, I'm under the understanding that this may not go away. The muscle that has been affected will remain affected. Eventually, Physical Therapy might help w/stamina. But everything will feel like a marathon. However, there are certain things she will have to pay attention to. For instance, she should keep herself warm. DM affects involuntary muscles, shivering works those muscles. Therefore, making you tired. Like a work out. And the thing is, she doesn't have to get cold enough to shiver. Shivering is a reaction to the slightest chill.
She will need to rest a lot as well. Another thing that takes getting used to if you've been active.
Since most of my pain is in my back, neck, and shoulders, sitting up, as aposed to standing or laying down, works those muscles. A long car ride wipes me out.
I do hope your wife will go into remission shortly.
She is very fortunate to have someone show interest in, and seek information about this. The more you know, the more you'll be able to understand and help her. Just having someone understand what you are going through is a big help. Help her to think positive. You will have to be patient as well.
Some other sites you might visit:
Give thanks in all things, for this is the Will of God!