As a NZ taxpayer she will be entitled to free public health care, irrespective of whether she has cover or not. This will probably also cover some physio and other allied health workers, although not if she sees them privately. The NZ public health care system is not in as bad a state as the NHS, and would give perfectly great care.
Winter travel insurance is probably cheaper if it's organised there, and she can shop around for better deals.
Hope she has fun!
beau