According to the Encyclopedia she was born in 3699 BBY, so she should be 57-58 in game time. She also looks around 50 in the game. But in Threat of Peace(around 10 years before the game story) her appearance and persona was not like someone who's 40, at most 25-30. Also she had become the youngest individual to assume the position of the Jedi Order's Grand Master in 3643 BBY, but that also brought a plot hole, she should be 56 at time. Nomi was clearly younger than that when she became the Grand Master, she was at most 30 during the Great Sith War and 40 in the end of TotJ.