See here for the full information.
https://www.immigration.govt.nz/new-...anent-resident
Yes, she can get a variation of her travel conditions, to extend them, so she can get back into NZ when she can get a flight. As you will see on that INZ page, how long an extension she can be granted will depend on her own circumstances - how long she had been in NZ, etc.. It's all there if you hit the links.
Once she is back in NZ, she doesn't need travel conditions. A residence visa gives the holder the right to live and work in NZ for ever.
When she wants to apply for PR, she needs to be aware that INZ count BACKWARDS from the date of application. So, using the 'time in NZ' criterion, she will need to have been in NZ for no fewer than 184 days in the 12 months leading up to the application, then 184 days in the 12 months before that. When she originally got residence is irrelevant - eligibility constantly shifts forward in time, so some of her first months in NZ will drop off the chart. She can apply for PR at any time when she can see that the numbers work in her case.