I'm a huge fan of Tolkien, and I had never heard of her. How bizarre. I wonder if she is mostly well known in America or whether I simply managed to miss her work. I am very tempted to get "The Atlas of Middle-earth" now though.
I'm only casually into LOTR, but I immediately recognized her name from my beloved copy of the Dragonlance Atlas. Quite fun to read how she basically invented the field of professional fantasy cartography.