Tracey is seen on board the Final Offer, protecting Penguin's safe room from Batman. She tries to send many men after Batman in order to stop him, but is eventually imprisoned in a cell in one of the rooms not long after trying to talk to Candy. She is next seen after Batman's fight with Deathstroke, in bed with Candy and Penguin.
It is assumed that she later quit Penguin's gang or was killed for some reason, as she is never seen or heard from again in later Arkham games.
Tracey's earned her status in Penguin's operation. Owing to a tough-as-nails, no nonsense attitude. Penguin uses her to keep his crew in line when he is not around. It's not clear why she has fallen in with Cobblepot. It's likely that the two met while he was living abroad. Perhaps he is grooming her to take over his operation someday. While she represents a minimal physical threat, she is as dangerous as anyone who picks up a gun and is willing to use it.