She was active in drama in high school and college before refining her talent at the Royal Academy of Dramatic Art in London.
[1] Jefferies was in the nine-hour trilogy of Horton Foote's Orphan’s Home Cycle in New York, directed by Michael Wilson, which won the Drama Desk Award for Theatrical Event of the Season of 2010.
She played Blanche in Streetcar Named Desire, Violet in Suddenly Last Summer, Hannah in Night of the Iguana, Carol in Orpheus Descending, and Amanda in The Glass Menagerie, which was among the Wall Street Journal’s best 10 productions of 2009.
She toured England in John Barton’s ten hour epic Tantalus, directed by Sir Peter Hall.
Her film credits include Hellion, Arlo and Julie, The Sideways Light, The Girl, Monsters, Violets Are Blue, and No Mercy.