Karla Five was a woman from the planet Arret in an antimatter universe encountered by the USS Enterprise in 2270. She had a son called Karl Four that was older than her, and her father (presumably named Karl Six) was an infant.
In 2270, she had accidentally traveled through a supernova to our universe. When attempting to return home, the crew of the Enterprise tried to stop her, believing she was bent on self-destruction. After they were pulled into her universe, she helped them return by allowing her ship to tow them at a higher speed than they could achieve by themselves. (TAS: "The Counter-Clock Incident")