Menu for Murder (1990)

Joanne Mayfield, head of the parental school commission, behaves like a dictator and makes all the other women her enemies. But when she suddenly falls dead on a party after having a sandwich, the main suspect is Susan, who served her the food. The handsome detective Joe Russo interrogates her repeatedly and they become friends. He invites her to help him with the investigation, what she happily accepts - too happily, says her husband.