The singer explained that it has been difficult to adjust to her sudden fame and described her success as a "whirlwind".
Jessie told Now: 'I'm ecstatic. I've found the attention a bit hard to get used to but it's been a whirlwind.
"About three years ago I had a record deal and I'd written an album. The single was ready to go, I was on a huge media campaign, but the record label went bust."
The 22-year-old said that her life quickly changed during a trip to the US.
She added: "I met people who liked what I did. The next thing I knew I was writing for different people and in the studio with Justin Timberlake."