Agatha Christie 
Case of the Perfect Maid 

When her maid asks Miss Marple to intervene in the delicate problem of her rather opinionated cousin Gladys, she doesnt think much can be done. Poor Gladys has been accused of stealing a precious brooch belonging to her employers, the reserved Misses Skinner. While one sister malingers with mysterious ailments, the other attends to her every need, and theyve both decided that Gladys must go. But, one day there appears a paragon to replace her, the perfect maid, or so they think.