Dead Shrinks Don't Talk by Sandra Gardner

When Marabella Vinegar finds her psychotherapist's bloody corpse, she becomes the NYPD’s perp of choice. Her recently deceased mother—the bane of her existence in life—comes back as a ghost to help get her out of trouble and find the real killer. Things get even worse when, thanks to Marabella and her mother’s sleuthing, someone tries to kill her. Then another body is found and Marabella is thrown in jail, awaiting trial for two murders. Can she and her mother-the-ghost-detective find the killer before Marabella becomes corpse number three?