I shopped regularly at a shop on Moreno Blvd. They were knowledgeable and helpful. They also had an indoor range and rented many types of common hanguns. I left San Diego in 99 but they should still be there. I wish I could remember the name and cross street. They were right down the road (100yds?) from a VW dealer, and just across I5 from mission bay park where the big hotel is. About 1/2 a mile South of the Clairmont exit.
I'd take mom down to use the range before buying. This way mom can test drive a few berfore you purchase.
ETA on a whim I looked in my files for an old receipt and here is the name.
Dunn's discount guns and sporting goods.
1510 Morena blvd suite F
SD, CA 92110
619-276-8736 This # is from before the 619 area code split so it may not be good.