The supermodel who attended Monday night's Metropolitan Museum of Art Costume Institute Gala in New York - had been asked by lover Jamie Hince to fly out to the US city early so she could watch him play with his band The Kills.
However, the British beauty refused and instead chose to spend time with Sir Philip Green, owner of British high street chain Topshop, on his luxurious yacht.
A source told Britain's
newspaper: "Jamie was gutted. He's been on the road for a month and really wants to see Kate.
His band had a show at the Webster Hall on Friday and he'd asked Kate to come to it because she was going to New York on Monday anyway.
"But she didn't want to make time to see him and went on Philip Green's yacht instead."
Jamie - who began dating Kate in 2007 - had also asked Kate to attend his concerts in Washington over the weekend, but she also snubbed his invite to those performances.
He is now asking her to accompany him when the band go to Canada, but it is believed Kate will once again refuse to attend.
A friend of the model said: "He is trying to get her to go to the Canada but it's not looking good."
Meanwhile, Kate, 35, made sure she enjoyed herself at the exclusive Gala - co-hosted by Kate, fashion designer Marc Jacobs, singer Justin Timberlake and US Vogue editor Anna Wintour - and after a few glasses of champagne she performed an impromptu duet with Kanye West to his hit
An onlooker revealed: "Kate loves the song. She went over to say hi to Kanye and they both started rapping it together."