She studied at the University of New South Wales, winning the Sir Kevin Ellis Prize for the best performance in the combined commerce and law degrees and graduating in 1991.
She later funded scholarships for the dux and best-performing female student of Bellingen High School.
She was seconded to London law firm Kingsley Napley from 1995 to 1996.
She also served as chair of the Education Committee of the New South Wales Bar Association.
Rees' appearances as a barrister included the Special Commission of Inquiry into Acute Care Services in New South Wales Public Hospitals (2008), Royal Commission into Institutional Responses to Child Sexual Abuse (2014) and Royal Commission into Misconduct in the Banking, Superannuation and Financial Services Industry (2018).