The X Factor finalist will release 'You Bring Me Joy' as her first official single on August 26.
The song will be released through Sony Music and Xenomania after the star signed a reported three-album deal with the label earlier this year.
The leaked version is 2 minutes, 53 seconds long, whereas the official single version clocks in at 3 minutes, 51 seconds.
Lily's debut album will follow in November, with the star expected to support the record with a performance on an X Factor live show.
Lily finished third on the 2011 series of The X Factor and was mentored by Destiny's Child member Kelly Rowland.
The pair have since recorded a duet together, but it is uncertain if the song will be included on either of the artists' future releases.
Listen to Amelia Lily's 'You Bring Me Joy' below: