If you think a joint gift would work, both of them might enjoy a scrapbook that celebrates her life. Depending on how many photos you might be able to collect, you could do a large, 12X12 album, or a simple 7X7 or 6X6 album. My favorite albums for gift-giving are the Creative Memories 7X7 books (I used to be a consultant), but Hobby Lobby or Michael's should have plenty of albums to choose from. There are 12 pages and it takes about 2 hours to completely fill and decorate it (there are even kits with pre-cut paper and embellishments designed for the smaller albums). The small albums hold one or two pictures per page. The larger albums can do anywhere from 1 to 5 pictures per page depending on how much writing and decorating you do. I'm pretty simplistic on the decorations, and like to have plenty of room to tell the stories that the pictures represent, so I usually do 3 to 5 pictures on a page in the larger albums.
You could talk to different friends and/or family members (especially those who are in photos with her) and ask them to say what they enjoyed about her, and use their words to write on the pages.