Parliaments have rules dictating behaviour for good reason. If they don't then discussion break down into chaos. So should they be punished? Absolutely.
The severity of that punishment depends on the type of haka and what was intended by it. In all the coverage I've seen no translation of what was said. A haka can be anything from expressions of joy to a declaration of war.
If the point was to intimidate or worse, then throw the book at her. Just as someone using intimidating or violent language would be ruled against. Doing it in a way specific to a particular culture does not get you protection.
If it was just a display of Maori culture at a poignant moment, expressing grief at the decision, then more leniency can be shown. However I doubt that's the case given the physical actions involved.