Nicole Scherzinger has experienced "a torrid few days" with her boyfriend Lewis Hamilton.
The 34-year-old singer is currently a judge on The X Factor UK.
While a contestant performed Cher's hit song Believe, Nicole couldn't repress her distress any longer and reportedly started crying.
"Three make-up artists rushed on to the stage to sort her out as all her make-up had run," a source told British newspaper The Mirror.
"She was clearly very upset and it's little wonder as it's been a torrid few days for her. But she's a true pro and just got on with things.
"But it's clear things are very testing for her at the moment."
Car racer Lewis was pictured with a group of women early Wednesday morning at the Mayfair Hotel after partying at the Funky Buddha nightclub without her.
Nicole was enraged when she saw what he was up to in the absence of her presence.
"[She's] absolutely livid [with Lewis and his] disrespectful attitude," the source added.
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