Bettan was a young female Thal soldier affiliated with the ruling Thal council at the time of the creation of the Daleks.
When Davros sent his Daleks to attack the Thal city and exterminate its inhabitants, the Fourth Doctor helped Bettan escape to safety. Together with some surviving members of her race, Bettan set up explosives outside the Kaled bunker with the intention of sealing Davros and his Daleks underground. With the Doctor and his companions, they watched on a monitor at the bunker entrance as Davros' creations turned on and apparently exterminated him. With Davros seemingly dead and the Daleks entombed, the Thals left to try and rebuild their society as the Doctor, Sarah Jane and Harry used the time ring to leave Skaro. (TV: Genesis of the Daleks)