Sweet Revenge.

While a major in the U.S. Army, Joe Cheever has a fling with his commanding officer's daughter that results in a pregnancy. Cheever convinces the girl to have an illegal abortion. The abortion goes wrong and the girl dies. To protect his career, Cheever implicates Captain Dennison whose life is thereby ruined. Years later, the Captain's now grown-up sister Katherine marries Army Major Alex Breen, and is stunned to learn his commanding officer is the now Colonel Cheever. She becomes obsessed with getting revenge for the sake of her dead brother.