She will be there on behalf of the Kotuku Foundation Assistance Animals charity, and will have her own assistance dog Rica there to calm her "huge anxieties" and PTSD the crowds will trigger.
"You can imagine what it takes to screw up the courage to be in a very crowded terrifying situation, but I just had to be there," Donne said.
"When we heard the royal couple were coming of course we applied to Internal Affairs, and I said to them it's lovely to see this isn't a tour crammed with visiting exclusive high class lodges and wineries where the average Kiwi wouldn't see the light of day.
"But they're actually getting out and about and meeting with grass-roots people. Of all the members of the royal family, Harry is the one that just strikes me as being entirely down to earth."
Rounding out the Wellington leg of the tour, the royal couple will visit Courtenay Creative to talk with young resident artists who will show off a wide array of work in make-up, live sculpture, costume, and virtual reality.
Courtenay Creative director Kristy Grant said all the artists and students "sort of consider these guys to be the cool ones, that's what everyone keeps saying".
"Although there's quite strict protocol about what we're able to do, the artists are quite relaxed about their interaction with them," Grant said.
"They feel you'll be able to talk to them and have an open conversation. They've been on a big tour so we want it to be relaxed when they come to see us."
One other noteworthy location Harry and Meghan are set to visit on Tuesday is the Pillars charity in Auckland, who mentor children with a parent in prison.
For their wedding present to Harry and Meghan, the New Zealand Government gifted $5000 to Pillars.
Chief executive Verna McFelin wonders whether Harry's support for the more "hardcore causes" such as the Invictus Games and Pillars comes from his mother, Princess Diana.
"The staff are thrilled. It's been difficult for the leaders in the organisation because we haven't been able to disclose any of this until the Prime Minister gave the announcement. But everyone's buzzing at the moment.
"These children are just over the moon they're going to meet someone so famous, so I think it's really special for our children, who suffer a lot from stigma and shame."
Harry and Meghan spent yesterday in Sydney for the final day of competition in the Invictus Games, after a tour of the Pacific including Tonga and Fiji.
