He's dating a runaround Sue and doesn't realize she won't settle down.
Он встречается с ветреной девушкой и не понимает, что она не захочет остепениться.
Definitions
Runaround Sue is a phrase popularized by the 1961 hit song of the same name by Dion. It refers to a woman who is perceived as unfaithful or flirtatious, often moving from one romantic partner to another and not staying committed to any one person.
