Taking into consideration her age of eighty-years, and co-morbid factors of arterial hypertension and hyperlipidemia, my recommendation would be Ativan - 0.25 mg, q.h.s. initially, titrating the dosage upward in 0.25 mg increments as-needed and as- tolerated.
Ativan has no appreciable effect on liver function (unlike Lexapro), Ativan would not accumulate excessively in the elderly (unlike Klonopin or Valium), and Ativan would provide guaranteed relief. Lexapro may prove to be overly stimulating. Lexapro is better suited for anxiety that recurs secondary to a depressive affect.
Serax is another (weaker) option. Speak with the neurologist.