The 21-year-old pop star wrote a track with the One Direction heartthrob last year, and while she found it exciting collaborating with the musician, she admitted it was a scary experience because he is so famous.
Recalling the moment she sang a rough demo of the song for the star, she said: ''Performing a love song in front of Harry is terrifying, and on top of that I was a little nervous because he was one of the first celebrities I met.''
However, the 'All About That Bass' hitmaker - who released her debut album 'Title' earlier this year - confessed the 21-year-old singer's contribution to the track was ''incredible''.
She continued: ''Harry was super talented at writing, and his lyrics were incredible - probably my favourite lyrics in a song. I remember I wrote it at midnight the night before and sent it to my mom. I was so worried he was going to hate it.''
Despite revealing it is one of the best tracks she has ever written, the blonde beauty has been left disappointed as no one has chosen to sing the song.
Speaking to Teen Vogue magazine, she added: ''It's a cute little number called 'Someday Maybe'. It needs a good home.''