Prior to entering politics, Collins worked as a commercial lawyer and was President of the Auckland District Law Society and Vice-President of the New Zealand Law Society. She was a solicitor for four different firms from 1981 and 1990, before running her own practice for a decade. She was a director of Housing New Zealand from 1999 to 2001 and worked as special counsel for Minter Ellison Rudd Watts from 2000 to 2002, before she entered the New Zealand Parliament at the 2002 election.