What do G.G. and Gaustine come to realize about Mrs. Sh.'s fear of showering in the novel, Time Shelter?

Mrs. Sh., a patient at the clinic, attracts G.G.'s attention because of how she reacts to the rooms at the clinic. Her refusal to take a shower is especially puzzling to G.G., and he soon realizes that it is the shower that is triggering her trauma. Further investigation reveals that Mrs. Sh. survived Auschwitz.