As a teenager, Rexha submitted a song to the National Academy of Recording Arts & Sciences ' annual "Grammy Day" event. Rexha earned the "Best Teen Songwriter" award, beating around 700 other entrants.    She would later come into contact with talent scout, Samantha Cox, who convinced Rexha to enroll in songwriting classes in New York City. At the time, she was 15 years old and took the classes with men in their 40s.  
Rexha's career began after she had a chance encounter with Fall Out Boy bassist, Pete Wentz , at a New York City recording studio in 2010.   She would eventually become the lead vocalist of Wentz's new experimental project, Black Cards . The band played a variety of live shows and released several singles and remixes. In January 2012, however, Wentz announced that Rexha had left the band to pursue other endeavors. 
On March 21, 2014, Rexha released her debut single " I Can't Stop Drinking About You ."  The song peaked at number 22 on Billboard ' s Top Heatseekers chart.  The music video for the song was released on August 12, 2014 and was inspired by imagery from films like Girl, Interrupted and Melancholia .  Rexha released two more singles, " I'm Gonna Show You Crazy " and " Gone ," in December 2014.   Her debut EP was released through Warner Bros. on May 12, 2015 and was entitled I Don't Wanna Grow Up .