Jessica Green is an actress who is still in the early stages of her career. She started acting in 2012 (at least that's when her first credit shows up), and has since had regular roles in 'The Outpost,' and 'Roman Empire.' Fans of the Evil Dead series may have seen her on an episode of ''Ash Vs Evil Dead' too. She is Australian with those deep blue eyes, and she's even pretty tall at five foot nine inches. As far as body type and look, she could definitely play Wonder Woman.
Since she is still in the relative early stages of her career, producers most likely couldn't take her seriously enough yet for the role. Producers have to take many things into consideration, including how the audience will react to the casting. Casting an Australian actress without any massive credit may have not been the most buzzworthy casting.