The best medications for anxiety disorder, are members of the group of anti-depressants starting with Prozac and continuing with all of Prozac’s progeny. The other medications, valium. etc., can be useful in the short run, however they must be used with caution, particularly with older folks.

It's case by case, but usually the SSRI family is a good option to start.

Generally reassurance is the best medicine. Communicating with your mother about her fears may be very beneficial. I would delay the use of medications because of potential dependency issues and/or side effects.