Elsewhere, Ireland's King took the women's breakthrough award having only made her international XVs debut in September.
New Zealand flanker Wallace Sititi won the men's breakthrough player award.
King won four caps and impressed during a WXV1 campaign that saw Ireland finish second, including a famous win over world champions New Zealand.
She also represented her country in Sevens at the Paris Olympics, and ended up going viral on social media.
During a restart in their match against Team GB, she held team-mate Emily Lane above her head, external, using her strength to prevent Lane from falling backwards before bringing her back down with the ball.