Pretty much the only thing I relate Kim Darby to is True Grit, but I have seen her on a particular ep' of Gunsmoke. One of those episodes where it seems like the regular cast barely shows up and the guests do all the heavy lifting.
A very handsome James Stacy was the confident male to Kim's sweet-natured young lady.
Maybe Darby didn't have a lot of range, but she played sweet so well. I found her so beguiling in this episode. Her hair was long and brown, and her face shined with earnestness.
Somewhat the same character as in True Grit, but w/o having to be defiant and with a better hairstyle and clothes. Just thinking of some of the shots of her make me smile, she's so pleasant and pretty. I hope she's still around and gets my little fan letter.