The 35-year-old actress is playing Cathy opposite Jacob Elordi as Heathcliff in Fennell's new big screen adaptation of Emily Bronte's 1847 romance novel of the same name.
Robbie - who is also producing - and Fennell focused on what would be sexy to women in their 30s and older when developing the script and the love scenes.
Speaking in the new issue of Vogue magazine, Robbie said: "What reads to us as hot or exciting or sexy?' And it's not just a sex position or someone taking their shirt off. It was the little things that we loved as two women in our 30s, and this movie is primarily for people in our demographic. These epic romances and period pieces aren't often made by women."
Robbie is aware that people will expecting this adaptation of Wuthering Heights to be "very raunchy" because of Fennell's previous work on TV series Killing Eve and films Promising Young Woman and Saltburn.
The Barbie actress insists there will be love scenes but the pair's vision for Wuthering Heights is to make an "epic romance" that will captivate audiences like James Cameron's Titanic (1997) and Baz Luhrmann's Romeo + Juliet (1996), the latter film Fennell was obsessed with growing up.
Robbie explained: "Everyone's expecting this to be very, very raunchy. I think people will be surprised. Not to say there aren't sexual elements and that it's not provocative - it definitely is provocative - but it's more romantic than provocative.
"This is a big epic romance. It's just been so long since we've had one - maybe The Notebook, also The English Patient. You have to go back decades.
"In one of our first conversations about this film, I asked Emerald what her dream outcome was. She said, 'I want this to be this generation's Titanic. I went to the cinema to watch Romeo and Juliet eight times and I was on the ground crying when I wasn't allowed to go back for a ninth. I want it to be that.'"
Wuthering Heights hits cinemas in February.
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