Today I got a response from Air New Zealand, here it is in full:
Good Morning Mr Leow,
Thank you for your email received.
It was very concerning to read of your experience onboard during your flight to Wellington.
To read of your wife falling sick during turbulence is a discomforting experience in itself. I appreciate the disappointment you felt with the performance of our crew at this time. I apologise the action to rectify your situation at the time was not sorted in a hasty way.
A rubbish bag would have been the convenient thing to bring to you for the sick bag, and some cloths to help clean up and for your wife as well. It clearly seems our crew member did not utilise any common sense in this occurrence or empathy for your wife.