The 'How We Do' singer and the Scottish DJ ended their nine-month relationship earlier this week, but it is believed their romance took a turn for the worse at the end of last year.
The 23-year-old singer flew out from the UK to see her beau ahead of his gigs in Puerto Rico, the Dominican Republic and Las Vegas in December, but the surprise visit didn't go down well as their confined company led to a number of heated rows.
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 flew to Vancouver on Tuesday (14.01.14) to begin shooting for her role in 'Fifty Shades of Grey', and she was previously rumoured to be moving in to Calvin's Beverly Hills mansion during filming.
However, since their relationship turned sour, the blonde beauty is believed to be staying in a hotel.