She represented Gibraltar at the 2010 Commonwealth Games in Delhi, India and competed for Team GB at the 2012 Summer Olympics in London, United Kingdom.

Cassar was born on 9 September 1993 in Welwyn Garden City, United Kingdom[1] to Maltese father Franco and English mother Jackie.

While there, she studied A-levels in psychology, biology and PE at King Edward's School.

[8] Cassar competed for Team GB at the 2012 Summer Olympics in London, United Kingdom.

[4] She could not represent her native Gibraltar because the Gibraltar Olympic Committee is not recognised by the International Olympic Committee; however, using a similar by-law to Anguillan long jumper Shara Proctor and Turks and Caicos Islander Delano Williams, Cassar was eligible to represent the United Kingdom as Gibraltar is a British Overseas Territory and so she holds a British passport.