The 'How We Do' singer and the Scottish DJ called time on their nine-month relationship earlier this week, but it is believed their romance actually hit the rocks at the end of last year.
The 23-year-old singer surprised her beau by flying out from the UK to see him ahead of his gigs in Puerto Rico, the Dominican Republic and Las Vegas in December, but their confined company caused heated arguments and bitter behaviour.
A source told The Sun newspaper: ''The rows escalated over New Year and Rita ended up sharing a room with a friend.
''Things changed between them and after New Year's Eve in Vegas, Rita was telling friends that she was single again.
''She is pretty cut up about everything but is throwing herself into work.''
Rita - who flew to Vancouver on Tuesday (14.01.14) to begin filming her role in 'Fifty Shades of Grey' - was rumoured to be moving in to Calvin's Beverly Hills mansion at the end of last year in order to make their long-distance relationship easier.
However, the blonde beauty is now living in a hotel after being kicked out of her London flat last year for making too much noise.
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His wife is on the warpath now.