I wouldn't get too focused on the short aspect. Find the right mattress for her. Different people find different mattresses comfortable. Go to REI (or a similar store that lets you try out mattresses) and try out all the different styles they have and see what she likes best. Be careful to not over-inflate the mattress. Letting a bit of air out helps. I think carrying a small piece of foam to add comfort around the hips is probably a good idea.

If you are camping on sandy soil dig out a depression to align with her curves before you set up the tent.