Byrnes was born in Australia and trained in all aspects of dance at the Bradshaw Dancers Performing Arts Academy from the age of four.
She attended Terra Sancta College in Quakers Hill, a suburb of Sydney, during her high school years.
One of her latest roles was Charlotte Watsford on Network Ten's H2O: Just Add Water.
Byrnes' first theatrical role was in Babe, where she played the Hoggetts' spoiled granddaughter.
In 2008, she was nominated again for an AFI Award (Best Supporting Actress in a television drama) for her performance in H2O: Just Add Water.