- Was named after actress Hayley Mills.
- Father is part Native American and works as a shaman.
- Her first acting job was in a Pringles commercial.
- Turned down an offer to study theology at Oxford in favor of studying acting.
- Played Catherine in a 2009 production of Arthur Miller's A View From the Bridge at London's Duke of York's Theatre.
- 2014, Olivier Awards — Best Actress: Nominee
- 2011, Golden Globe — Best Performance by an Actress in a Miniseries or Motion Picture Made for Television: Nominee
- Gabriel Bisset-Smith — Ex-significant Other
- Alison Atwell — Mother
- Grant Atwell — Father
- Guildhall School of Music & Drama, London, England (2005)