But this week the British actress was not shy in showing how smitten she is with her new man Louis Dowler.
Stepping into the spotlight together at the San Sebastian Film Festival, the couple couldn’t keep their hands off each other as they attended the first red carpet event of their relationship.
Kate, 34, sizzled in a super-sexy LBD-and-heels-combination and with a mega-watt smile as she went public with model Louis, spending much of the night gazing into his eyes.
Click on photos for gallery
The pair stuck close throughout the evening as they mingled with Julia Roberts and Javier Bardem, who are also at the festival.
Kate and Louis – who has starred in high-profile campaigns for Burberry and Paul Smith – confirmed their romance back in August when they were seen hand-in-hand during a night out in London.
They were first linked earlier that same month when pictures emerged of the pair exercising together in the Big Apple.
According to friends, they have become inseparable – to the extent that Kate is loathe to leave Louis, also 34, behind when she heads to Chicago to film her new movie Contagion.
"Kate hates the idea of having a long-distance relationship, even for a short period of time," a source close to the actress has revealed.
"They have discussed the idea of Louis going with her while she films so they won't have to endure a long-distance relationship at such an early stage in what seems to be something pretty serious.
"Kate hasn’t been this happy in a very long time."
While in the Windy City filming the medical thriller – also starring Matt Damon, Marion Cotillard, Gwyneth Paltrow and Jude Law – the Oscar winner will arrange care of her two children with ex-husband Sam Mendes, who lives in New York.
They announced their separation after seven years of marriage in March this year. Kate and Sam are parents to son Joe Alfie, six, and the star also has a daughter Mia, who will be ten next month, with her first husband Jim Threapleton.