I do wonder how and why Monica Rich was cast. Aside from a 1967 appearance on NET Opera Theater, she has no acting credits either before of after NODS. She's okay in the movie. Just okay. But there were surely other actresses in that age group who could have given a stronger performance. Did her family have some sort of connection to DC? Or was she simply willing to work for the salary that was being offered?
I have heard stories over the years that DC was not satisfied with her performance. It's very telling that DC would allow the unprofessional behavior of Roger Davis but not for an unexperienced child.