This did not wash with Opposition MPs who argued that she was obliged to name the official because taxpayers had funded the visit. With whom she had met or dined was therefore a matter of public interest.
Labour deputy leader David Parker suggested to the Speaker, David Carter, that question time in Parliament was an important element in ensuring ministers were held to account for such spending. Ministers should therefore take questions seriously and endeavour to give informative replies.
Carter, however, ruled that Collins had addressed the basic question Parker and his colleagues were asking. "The minister has answered by saying she cannot answer that question.''
Labour's Grant Robertson - who has been leading the Opposition offensive against Collins - said taxpayers were entitled to "have some honesty from the minister for once''.
But Collins retorted that it was a private dinner, "and as that member might one day find out, even ministers are allowed to have private dinners with friends''.
But that was not the issue yesterday. What was worrying Opposition parties was that Collins' refusal to name the official might end up setting a precedent.
Labour's Trevor Mallard asked whether Carter was making a new Speaker's ruling that a minister could decline to answer a question because it was in his or her private interest not to answer it.
But the Speaker assured Mallard - to Mallard's and other Opposition MPs' relief - that he was not saying that at all.