They were together on the 'On The Road Again Tour' between June and October last year.
According to a source close to Smith, the American flight attendant also flew to London to see Styles earlier in the year and had planned to visit again, reports dailymail.co.uk.
"He (Styles) supported Megan through some tough times in her life and started referring to her as his girlfriend," The Sun newspaper quoted the source as saying.
"Megan never asked him about other women because she accepted he was a rock star but she was madly in love and believed Harry felt the same," the source added.
Their romance is believed to have ended after a steamy photograph sent to the star began to circulate on the internet, prompting him to believe that their tryst would be discovered.
"Harry started hearing there was a chance the relationship would go public and he decided it was the right time to end things," the source said.
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