Avalon's early history is unknown. By the time of her encounter with Blake on the Liberator she had started resistance groups on a dozen planets. At some point she had encountered Jenna. Cally had long been an admirer of her activities.
Avalon was working on an ice planet when increased Federation activity forced her to ask for Blake's help in relocating to a safer planet. This was part of one of Travis' plans: Avalon was betrayed by her follower Terloc and captured.
The Federation had constructed an extremely advanced android replica of Avalon and planned to use it to capture the Liberator intact. Blake and his crew were allowed to 'rescue' the android, and the plan was for the replica to release a lethal virus on the ship, killing all on board.
The android was discovered before the virus could be released and Blake was able to use it and the virus to bargain for the real Avalon's life. She left the planet with Blake.
Her activities after this are unknown.