The couple broke off their engagement in December, allegedly over her "demanding" career goals.
Speaking after a number of live dates in the UK this week, Jenkins admitted that she is still struggling to perform some of her more romantic tracks.
"I sing from my heart so it's been difficult to sing love songs. Those songs were written before everything happened," she told The Mirror. "I got really emotional at the end because I know the journey I've been on."
The publication also quotes her as telling fans at a concert on Thursday (February 16) that they had "mended her heart".
She continued: "When I first started this tour I was a bit of a mess. I didn't know how I was going to get through it. I looked at my list of songs and they're all about love and heartbreak... But that's my problem."
Jenkins, a formerly prolific Twitter user, only returned to the site for the first time since her split last month.