Cold But Not Forgotten

Lieutenant Carson, a rural Nevada detective, discovers a woman's lifeless body while at the shooting range with his team. The dead woman is covered in blood-although her corpse reveals no apparent wounds.
As Carson delves into the case, he encounters an interwoven web of suspects. Her dentist husband is having an affair with his office manager, who has been embezzling from him. A marathon partner is jealous of Diane's trophies. Her doctor has been giving her arsenic to scare her into eating better. Kindly Mrs. Howell, a widowed neighbor of the victim's, had access to her computer and detested the husband.
Everyone says she's the nicest lady in town.
So who would want to kill her?