The Deception star appears in some steamy scenes with Gosling in their eagerly awaited new drama Blue Valentine.
And in a recent interview with USA Today, she mischievously implied the two were a couple and that the on-screen sex was no act.
“We had a very good time,” she joked. “We rehearsed it. A lot. We really wanted to get it right. It was a really hard day at work.'
Williams added that their on-screen relationship also had some benefits off-screen.
'I put on some weight for this movie,” the 30-year-old Shutter Island star said.
“He would make me ice-cream shakes in the morning. So before the hot sex, he would feed me.
“How lucky was I?'