In the 1999 election, she was the Alliance's candidate for the Invercargill electorate, and was ranked twenty-second on the party's list.
Later, when the Democrats joined Jim Anderton to establish the breakaway Progressive Coalition, de Ruyter took an active role in building the new party.
By the time of the 2002 election, de Ruyter was deputy leader of the Democrats and was ranked fifth on the Progressive list.
Not long after the 2002 election, the Democrats opted to leave the Progressive Coalition and reestablish themselves as an independent party.
De Ruyter has also been involved in local-body politics in Invercargill, standing for election to the Southland health board.