Kate Winslet on Her Age Difference with Liam Hemsworth: 'I Didn't Know How Old Liam Was'

Kate Winslet knew very little about her The Dressmaker costar Liam Hemsworth – not even his age.

Winslet and Hemsworth talked to PEOPLE about their romance in their upcoming film at London Fog's special screening of The Dressmaker at Frances Gould Hall Theater in New York City on Friday night.

In the film, Winslet plays a couture seamstress who returns to her hometown to seek revenge against those who banished her when she was a child for her involvement in a fatal accident. Hemsworth stars as Teddy, a local who steals her heart. Winslet, 40, said the age difference between her and Hemsworth, 26, was not really a concern.

"It didn't even occur to me," she said. "And the funny thing is now that the film is coming out, people are noticing that. I'm like, 'Oh yeah, I completely, honestly, until today, I didn't know how old Liam was.' "

Her explanation? Winslet said she's not super into the Internet.

"I don't Google," Winslet said. "I don't have any social media of any kind at all. He was just Liam Hemsworth playing Teddy. Because the characters were contemporaries when they were younger, to me that was all we were doing."

One person who might have Googled facts about Hemsworth? Her 15-year-old daughter Mia Threapleton.

"She was just really jealous that I got to kiss Liam Hemsworth," she said, adding, "She couldn't come [to the set] on the days that he was there. She was mortified."

Hemsworth told PEOPLE he knew of Mia's crush, and talked about his anticipation to work with Winslet.

"I was very excited when I heard she was a part of the film, and that was a big attraction to do this," he said.

The Hunger Games star also talked about prepping for those NSFW romance scenes and his dentist-approved suggestion.

"Woah! Those are always – I don't know, what do you do?" he said. "Brush your teeth beforehand? That would be my only advice."