Because of episodes with Peter and Shera together, and people like John Cassavetes and Gena Rowlands (separately), I can't help wondering how many spouses of Columbo actors would've worked on the show.
They were already long divorced before Culp made his first appearance. He left his previous wife (and mother of all his kids) for Nuyen as a result of an "I Spy" they did. The marriage only lasted a couple years. When Culp did a commentary for that episode in the late 90s I think he kept referring to her as "Miss Nuyen".