At the age of one Clarke moved with her parents to Houston, Texas. At age 6 she moved to Woking, England, where she attended TASIS England before moving to New York City at age 11. The nickname "Emmy" is derived from her first two initials. She has two siblings, Patrick (older) and Bridget (younger). She now lives in Fairfield County, Connecticut.
Her first acting role was in the 2003 TV film My House in Umbria, for which she won the Best Performance in a TV Movie, Miniseries, or Special - Supporting Young ActressYoung Artist Award in 2004.