Well, believe it or not, yes... there ARE people who are so insanely jealous that they think simply singing a duet with another person consitutes a marital crime.
In this lady's putrid mind, I'm sure she thought he did the ultimate wrong.
(though, trying to run him down with her car....??.... yikes, that's a bit extreme)
11th Commandment:
Thou shalt not duet karaoke with a member of the opposite sex unless there is a line or two in the song for your spouse to sing as well.