Just found this site and offer the following:
The first person you may wish to contact is Janet Stessl in Chicago. She can be reached at janstessl@aol.com. Jan edits a Zither Newsletter and can provide strings, books and other materials.
If your Mother is interested, there is a Chicago Zither Ensemble that is the country's oldest continuously operating Zither "club". Philadelphia's Zither Ensemble has recently started meeting again. There is an active group of players that meet with Jane Curtis in Virgina several times a year. This April we established the National Zither Orchestra in Davenport, IA, with the assistance of Tomy Temerson of Hanau, Germany, and will meet in Davenport again every 18 months or so, the next meeting is in the Fall of 2009. A select group of players from the NZO plus some other professional musicians will be performing in Montrose, CO, in September. We are making plans to have a Zither workshop plus performances at the 2009 Gaufest which will be held in Toledo, OH. If your mother is interested in learning about any of the above, please let me know. Conversely, I have a young student who may need to purchase a zither. If you could share any information about the zither you purchased (what, where, how much, satisfaction level, etc.) I would greatly appreciate it. Concerning amplification, I have two contact microphones, one made for guitar and another by the firm AKC for "acoustic instruments". I use them both only for zither. My Gibson Les Paul and Fender Jazzmaster don't need anything but what they already have!