Also, have you ever tried swimming for exercise? It has the benefits of burning a lot of calories without bringing your heart rate (and out-of-breath-ness) up as high as the same intensity exercise on land.

My experience with swimming is that simply being in water strains your lungs more (as you have to displace water to inhale air). Simply going to the pool and talking to someone while in up to your neck is probably good lung training, but until she can do that comfortably and without attacks I would recommend against trying laps or other sort of exercise.