The 16-year-old climate activist made the comments during a recent interview on Scandinavian talk show Skavlan. Documentary maker Michael Moore was also a guest on the episode.
Thunberg revealed that she doesn't like small talk - or many people - which spurred host Fredrik Skavlan to ask her whether that was the reason she 'didn't go up to Trump at the [recent United Nations climate conference] for a small chit chat'.
Greta .v. POTUS
"Maybe not the biggest reason," Thunberg answered, prompting laughter from the audience.
"But I do cancel meetings with heads of state because I don't want to make small talk with them - because I know all it's going to be about."
Asked what she was thinking during the now-famous moment she gave Trump an angry stare, Thunberg said: "I was shocked because suddenly security came in and said 'you have to step to the side'. I wondered what was going on, then he showed up. I think he was very shocked."
'A very happy young girl'
After Thunberg's emotional speech at the United Nations Climate Action Summit, Trump retweeted a WIRED article which quoted Thunberg talking about the devastation of climate change.
Trump wrote: "She seems like a very happy young girl looking forward to a bright and wonderful future. So nice to see!"
Speaking about what appeared to be a sarcastic comment, Thunberg said: "You can interpret it in many different ways, but I knew that at some time, he was probably going to say something about me, and it doesn't make any difference."