She was due to fly Wednesday to film a TV special at the beginning of a 10-week stay.
"She cancelled her trip and all work commitments in the UK at the very last minute, which is very unlike her. She has been hitting it hard for months. She smokes, drinks and parties hard on top of work commitments," thesun.co.uk quoted a source as saying.
Management of the 24-year-old cited sickness for her axing of the TV show.
She herself hasn't commented on her cancelled trip, but posted a message on Twitter Wednesday.
"Keep your eyes on the finish line and not on the turmoil around you #thinkahead (sic)" she tweeted.
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