Born on a failed Federation colony that turned to crime, Yar escaped and joined Starfleet and eventually became security chief of the flagship, Enterprise.
The character of Tasha Yar as security chief was a strong one that should have continued. There was one episode where she was a member of a team engaged in an extremely physical contest and Worf was a member of her team. Clearly, he considered her an asset in the contest, which was a demonstration of her physical prowess. Women that made their way onto Star Ships had to have some physical ability to go along with their mental and psychological capabilities.
Nothing wrong with Denise Crosby's acting as the security officer Tasha Yar, but the whole alternate universe, half-Romulan stuff was a bit much. Glad they killed her off. Although the character's fling with Data was hilarious!