home wrecker

noun1

1. •
   (slang, offensive) A person who gains the affections of someone already married or engaged, and thus causes the dissolution of the marriage or engagement.

   • I, unfortunately, was the prey of a vicious, depraved B-girl. In addition, the proprietress is a Nazi. We barely escaped with our lives. Go investigate that gang and let us alone, you homewrecker. — 1963