You're in the SF Bay area which is a pretty big hub for for the Freshwater fish hobby. You're at an advantage because a lot of clubs are around and rarer fish arrive in the bay area compared to other areas.
Have your sister check out the aquatic clubs around. SVAS (Silicon Valley Aquarium Society
) is a south bay club. I dunno much about them but I know some members. I personally belong to SFAS (San Francisco Aquarium Society)
. Both of these clubs are very fish focused. They hold once a month meetings with guest speakers and auctions. Sometime you can get some pretty sweet deals on equipment, plants and livestock at the auctions, but it really varies from month to month.
Also take trips to the various local fish stores. You're in an area where you don't have to depend on Petspart. Most shops really take care of their stock and carry specialty items. I know of Neptunes in San Jose as a good place and I've also heard of Dolphin Pet Villiage.
SF has a higher amount of stores however my top two are Aquatic Centra
l and http://www.adana-usa.com/
. Aquatic has a solid selection and they do their best to keep their prices low. They are very helpful. Aqua Forest is very high end in terms of their equipment and style (they are the only retailer of Aqua Design Amano in the United States). However it's a wonderful place for getting inspiration on setting up a truly stunning setup and they also have some decently priced fish. Their specialty though is their large selection of aquatic plants. They have a lot of stuff you will not find out of a planted tank society (we have one of those
in the bay area too btw).
Hope that helps.