She was the script editor of the ninth, tenth and eleventh series of Thomas & Friends. Miller subsequently became the head writer for the series, starting with the twelfth series, and served as creative producer from Hero of the Rails, up until the fourteenth series. Additionally, Miller worked alongside Jo Jordan during the same series and Misty Island Rescue. In 2010, Miller stepped down as the head writer and was succeeded by Andrew Brenner. From Misty Island Rescue until the end of the show with the twenty-fourth series, she served as the voice director. She also provided the voice of Elizabeth II in Thomas and the Royal Engine. She also wrote the "Bob the Builder" episode "Roley's Rovers" and has written for "Mike the Knight" and "Lily's Driftwood Bay". She also currently voice directs and writes for "Wissper", and she also voice directed the Aardman stop-motion produced "Star Wars: Visions" episode, "I Am Your Mother".