|Swift and Styles|
A source close to the couple told The Sun newspaper: "Taylor knows she's far more high-profile in America and way richer, and saw her career as more important. She always brushed off his schedule and needs and put hers first.
"When he complained his bandmates were getting irritated and she should do more to make things work, they started to yell crazy things. Taylor even yelled he was lucky to be with her.
"There were also problems over commitment. Harry wasn't committed enough for her liking."
Another source agreed, adding Taylor, 23, had trouble trusting charmer Harry, 18, who is known for his flirting and womanising ways, having wooed TV presenter Caroline Flack and married radio DJ Lucy Horobin during his time in the boy band.
The insider told the Daily Star newspaper: "Taylor's been in the industry longer than Harry.
"She finds it embarrassing that he always stops for female fans posing for endless photographs and signing autographs.
"But she told Harry she thought it was really cheap. Harry's a happy-go-lucky guy and would never dream of snubbing fans.
"However, Taylor told him she didn't like him constantly chatting and flirting with girls.
"Harry's a cheeky charmer, he finds all the attention funny and flattering.
"A massive row erupted and in the heat of the moment Taylor really insulted Harry. She's not used to not getting her own way."
After their argument the couple ended their Caribbean New Year holiday and went their separate ways. Harry is now back in the UK rehearsing with One Direction, while Taylor has returned to the US.