Breen began her writing career on the tenth season of Frasier. She worked as a story editor on the eleventh and final season while also contributing two scripts. In 2006 she wrote a pilot script for ABC called Pink Collar starring Alicia Silverstone. The pilot was not successful in securing a series order. In 2009 she joined the writing staff of Big Love for its third season. She was a co-producer in season four and a producer in its fifth and final season. She contributed one script each season.