No, she wasn't the only Scottish singer, but in my opinion she was the finest vocal interpreter of Scotland's traditional ballads, jigs, and reels, as well as music based on the poetry of Robert Burns. I learned yesterday of her death on August 21.
I had the good fortune to see Jean Redpath in performance at a small venue near Washington Square Park sometime in the late 1970s. There were only about twenty of us in the audience. It was a magical evening.