The 'X Factor' judge and the Formula 1 driver called time on their five-year on/off relationship because working commitments meant they barely got to spend time together, but the 'Boomerang' hitmaker has been continuing to perform gigs to take her mind off the break up.
A source said: ''Nicole is heartbroken about the split. She thought he was 'the one' but it didn't work out.
''Yesterday Nicole had a gig in Sardinia. She is throwing herself into work to forget the pain of the break-up.''
While news of the break up has only just materialised this week, the pair are said to have gone their separate ways around one month ago.
The source added to The Sun newspaper: ''She and Lewis broke up around a month ago and have been keeping it quiet since then.
''Only a few close friends and family knew and they've been comforting both of them.''
The pair's split comes just two weeks after Lewis - who lives in Switzerland and travels around the world to compete in Formula 1 races - hinted he was going to propose to the 35-year-old beauty, who is based in the US and is reprising her role as a judge on 'The X Factor' in the UK later this year.
He recently said: ''We've been together for five years, which is quite a milestone really.
''But hopefully [I'll propose] in the near future before we get to six years.''
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