A Minister of the Crown, while holding a ministerial warrant, acts in a number of different capacities:
a. in a ministerial capacity, making decisions and determining and promoting policy within particular portfolios;
b. in a political capacity as a member of Parliament, representing a constituency or particular community of interest; and
c. in a personal capacity.
In all these roles and at all times, Ministers are expected to act lawfully and to behave in a way that upholds, and is seen to uphold, the highest ethical standards. This includes exercising a professional approach and good judgement in their interactions with the public and officials, and in all their communications, personal and professional. Ultimately, Ministers are accountable to the Prime Minister for their behaviour.
...and the Prime Minister is accountable to Parliament, and to the people.
Its fine for the PM to say that the Electoral Commission is investigating, and to withhold judgement until then. But its not fine for her to pretend its not her problem. And the longer she does, the more crooked she looks. But hey, if she wants to bleed out like Helen Clark defending the indefensible, then that's her problem.