She served as a Labor Party Member of the New South Wales Legislative Assembly from 1994 until 2003, representing the electorate of Parramatta.

In July 1993, Ziolkowski advised Leader of the Opposition, Bob Carr, that he had been diagnosed with a very rare form of cancer of the oesophagus.

[4] She was criticised by her opponent, Liberal candidate, Wendy Jones, for running for office instead of staying at home and looking after her son Tristan, then aged 7.

During 2002, Harrison (along with NSW Speaker John Murray) was sued before the Australian Industrial Relations Commission for A$800,000 by former staffer Anne Stonham, who claimed that her contract was "unfair" and she had been overworked.

Another staffer, John Cairn, accused Harrison of keeping photographs of her enemies in a locket around her neck.