Collin Wilcox ended up doing a lot of work in television as a guest star in a wide variety of shows that ranged from The Alfred Hitchcock Hour to Columbo, but it was live theater that was her true passion. I never saw her on stage, but from what I've seen of her work in movies and television, she must have been incredible.
She did appear in other movies, most notably, The Baby Maker with Barbara Hershey, but her work in To Kill a Mockingbird proved to be her most powerful film role. As for television, fans of The Twilight Zone may remember her from the classic episode, Number Twelve Looks Just Like You, where she played the young girl trying to hold on to her identity.
Collin Wilcox passed away in 2009 at the young age of 74, but her body of work lives on. If you take the time to discover her, you will find that the best actors are not always the famous ones.