Do I have to ship to Aussie if it is not a shipping option on my auction?

No, Australian buyers need to ask first, if you only have NZ options on Auction, If it is to be arranged they need to ask first before placing a bid or using Buy Now,

as a lot of sellers will not ship out of New Zealand, If sellers use Book a courier you cannot use it to send overseas etc.

Hi Sona. You can use this link to get the feedback removed. Hit "File a report" at the bottom

https://help.trademe.co.nz/hc/en-us/articles/360007264271-Disputing-feedback-from-the-buyer

Kia Ora Sona,

Sorry to read of your experience with that Trade,

You may like to include a note at the bottom of your Listing Description stating something like "Sorry No Shipping to Australia" - to help avoid this happening again. - Cheers.

I did some research 
Shipping & delivery information – Help - Trade Me

When you place a bid or Buy Now, you'll be asked to choose your destination and preferred service – if multiple are available.

If your delivery destination isn't available, ask the seller. Mention your delivery area, but not your actual address – anyone can see the Q&A.

You only have to ship to areas listed in your shipping destinations on your listing. However seending to Aussie is not as hard as you may imagine. NZ post website will do a complete international quote and you can buy the ticket there as well. You do have to take it in to your postal center though to send. I never list aussie shipping prices but have sent on request a number of times over the years.  The shipping price to aussie is a lot more than NZ of course, and once you quote that to the buyer its possible they will refuse to go ahead anyway

It's even easier now Don. You don't need to take to Post Centre. You can make a booking for the courier to come and collect it from you at the same time. Only applies to their tracked offerings of course. But you should use those anyway for your own protection when sending.