Director Nathan Grossman recorded Thunberg's everyday life for a year, chronicling her rise to fame from the beginning of her school strike outside the Swedish parliament in August 2018 to her trips around the world demanding that political leaders take action to fight climate change.
When he began filming, Grossman had no idea that Thunberg, who was 15 when she started her protest, would quickly become the figurehead for the global climate crisis campaign.
"I think we have seen a lot of her in the news media, she has been doing so many interviews and I wanted to bring the viewer closer to her, how does it feel to go from nothing to become this very famous climate activist," Grossman told Reuters in an interview on Saturday.
"I was also thinking like 'Jesus, everything is going so quickly. What a weird kind of rush ... this is' in a sense that we are standing here with the pope and just like eight, nine months ago she started the school strike," he said.
Thunberg, who appeared by video link on Friday at the Venice festival where the film, "I Am Greta", has been screened out of competition, said she was pleased with how she was portrayed.
"You did succeed in framing me as myself and not the person that the media frames me to be, not the angry, naive child who sits in the United Nations General Assembly screaming at world leaders. Because that's not the person I am," she said.
"So, I think he definitely made me seem like a more shy, nerdy person which is the person that I am."
She also said the documentary debunked some of the accusations of critics who say she is being manipulated by others.
"Some people say that, they spread conspiracy theories ... that I don't think for myself or I don't speak for myself or someone else writes my speeches ... In the movie you can see that that is not actually true and that I do of course speak for myself and I decide everything for myself."
Thunberg, who last month returned to school, said the fight against climate change, which has been overshadowed by the coronavirus pandemic, should remain a priority.
The Venice film festival ends on September 12th. - Reuters
