(I oppose Labour's anti-party-hopping law, but I'm happy to laugh at someone who hoists themself with their own petard like that).
Whaitiri was infamously sacked from Cabinet for bullying. Labour has since rehabilitated her - which you'd hope means there's been a change in behaviour - but she's also clearly at the bottom of the Ministerial rankings, the sort of mediocrity who will be dumped to make way for coalition party Ministers or new talent if Labour is lucky enough to be able to form a government after the election. Which makes her sudden switch seem opportunistic and driven by career ambitions, especially in the absence of any announced point of principle to justify the switch ("coming home to her whakapapa" is not a terrible reason, but seems a bit weak for this sort of sudden change). But I guess that's ultimately going to be up to the voters of Ikaroa-Rāwhiti to judge.