The 'X Factor' judge was recently left furious after her boyfriend was caught partying with 10 girls in his hotel suite last week.
"Nicole's confiding in pals that she thinks it might be time to call it a day. It's a long distance relationship, he isn't ready to settle down and they're both working non-stop - she's tired of fighting for it and feels it just isn't working.
"Nicole is so busy at the moment with promotional activity for her music on top of her role on 'X Factor'. It's really hurt her that she has to take on a new job while feeling so humiliated. She is furious he could be so disrespectful to her," a source said.