The 'How We Do' singer recently started dating the Scottish DJ and the couple are now said to be inseparable after spending the weekend in Las Vegas, where he was performing at the Grand Hotel's new club Hakkasan on Saturday night (04.05.13).
A source told the New York Post's Page Six: ''She was in the DJ booth during his entire performance and the two were seen getting really cosy and kissing.''
Another source told The Sun newspaper: ''It's early days, but they're keen on each other'', and revealed friends are already calling them the ''perfect couple.''
The 'Sweet Nothing' hitmaker, 29, posted a photo of Rita, 22, boarding his jet on Sunday with the caption: ''You again!''
The couple has also reportedly enjoyed a string of low-key dates at the Chateau Marmont hotel in Hollywood.
Rita and Calvin initially clashed last year when she revealed she rejected his track 'Call My Name' and he later dismissed her comment on Twitter, writing: ''She made that up.''
But the couple, who have several mutual friends including Ellie Goulding, appear to have put the incident behind them.
Calvin was linked to model Anne V in February, following her split from Maroon 5 frontman Adam Levine, but they recently ended their romance amicably.
Rita, who previously dated reality TV star Rob Kardashian, and was most recently linked to David Beckham's best pal David Garner.