She does really nice work, and her prices are really low (I think it should be selling for more).
Where I sell, it's pretty much all sci fi/ fantasy/ space/ horror themed work.
Her work has pretty broad appeal so I'd check out art fairs, regionally. Attend them to see if anyone is buying anything before committing. For fairs, make bookmarks or magnets or other impulse items that people can afford without thinking in addition to having the regular work plus a few expensive showpieces. If she doesn't already do art fairs I have a couple of friends who do them in addition to the con art shows and they could probably provide helpful advice and marketing, etc. if she's interested. They love to help and give advice so it would be no problem.
People are still buying art, they are just careful about getting value when they make purchases. The high end is diminished, inexpensive small items move at a fast pace. As with any types of shows, it's the people returning year after year that build the sales volume.