"Prince Harry is someone who is seen to be on a pedestal and for him to go up and say 'I've actually dealt with mental health issues, its not something to be ashamed about', will let millions of young and old people around the world know they are not alone.
"What he's doing is showing that mental health doesn't discriminate."
She said it was a good opportunity to discuss New Zealand's mental health system and what can be done to improve it.
"It's very public that we've got the highest suicide rate in the world but what is really good is while it's tragically high and there are systems that are broken, we have now decided as a country to have the conversations that matter.
"It's taken us a while but now things are moving forward which is really exciting."
Thornton said her experience with social media gave her a different perspective on how New Zealand youth deal with mental health problems.
"The majority of messages that come in to us from people saying that something has saved their lives is they've been in the darkness of their room and they are scrolling social media just mindlessly planning on taking their life.
"Social media can be a terrible thing, but if we can activate it for a great purpose, it can save a lot of lives without us being in the room with them."
Thornton said the mental health stigmas about how issues were attention-seeking and a waste of resources needed to change.
"Breaking the stigma and changing people's mind around the area of mental health is essential to enable the conversations to happen a lot earlier before the crisis actually hits."
The royal couple will be coming to New Zealand on October 28 until November 1 visiting places including Wellington, Abel Tasman National Park, Auckland and Rotorua.
Royal itinerary
October 28
Arrive
Welcome at Government House
Wreath-laying ceremony at Pukeahu National War Memorial Park
Reception hosted by the Governor-General
October 29
Visit Maranui Cafe at Lyall Bay
Travel to Abel Tasman National Park
Beach barbeque with school children
Return to Wellington for an encounter with young people
October 30
Travel to Redvale on Auckland's North Shore
Join children in a gumboot throwing contest
Visit Pillars, which supports children with a parent in prison
Wander around Viaduct Harbour
Reception hosted by the Prime Minister
October 31
Visit Te Papaiouru Marae in Rotorua
Check out Rainbow Springs
Public meet and greet Rotorua Government Gardens
Visit Redwoods Treewalk
Return to Auckland
November 1
Leave
Best places for a glimpse
Auckland's Viaduct Harbour on the afternoon of October 30
Rotorua's Government Gardens on the afternoon of October 31