http://www.bayphoto.com/show-sell-photos-online/imagequix.htm (NOTE, I'M IN CANADA HAVE NOT USED THIS U.S. SITE!!) Bayphoto is pretty popular with pros. This is their page about galleries. Looks like they have a pay-as-you-go plan, so you don't have to get a gallery for a month or a year.
Or, you could make your relative buy you a Pro SmugMug account for a year and their pro account uses Bay Photo. Then you would have the gallery for other things. They have a cheaper option, but the printing is done at a cheaper lab.
OR if your relative pays for the $30 Smugmug account, you can upload everything into a password protected gallery and she can download the files she wants to carry off to her local lab.
Millers lab is another that I've heard raves about, you'd have to check if they have galleries though. (I've even discussed Millers with my pro lab in Canada and they seem to watch them for trends).