An allergist would be best equipped to answer this
Hepa filters work wonderfully, however since she has problems traveling she would have to buy a small unit for travel for that to work. There are lots of other life style opions as well - keeping doors and windows closed, showering and changing clothes when she comes in and before bed, allergy proof cases for mattress, boxsprings and pillows, keeping pets out of the bedroom and eliminating as many dust collectors from the bedroom as possible (blinds, drapery, upholstered furniture, plants...). Also, keeping the bathroom mold free is very helpful.
I hope you find alternatives for her tha will work with your life style.