Summary from Goodreads:

BITTER HARRIDAN...

Few tears fall when rich, spiteful old Mathilda Gillespie's bloody corpse is found in her bathtub, her wrists slit and the ancient scold's bridle clamped on her head. It seems Mathilda's favorite heirloom was also an instrument of torture from the Middle Ages, an iron cage used to gag yapping women. Among the Dorset villagers, only Sarah Blakeney, Mathilda's doctor for her final year, seems even mildly disturbed that the miserable nag has been muzzled forever.

OR TRAGIC VICTIM?

But suicide starts to look like homicide, and Sarah's sorrow seems a bit contrived when the bombshell drops that Mathilda has disinherited her daughter and granddaughter, leaving her entire fortune to Sarah.

Now the object of vicious gossip and the police's prime suspect in a brutal murder, Sarah must prove her innocence by delving into Mathilda's past to unmask the real killer. What she finds beneath the sleepy village facade is a grisly potpourri of blackmail, butchery, and perversion.