What is the significance of Liesl to Dunstan? Also, how does Robertson Davies empower her in Fifth Business? Please provide quotes and evidence.

More than any other person in Dunstan Ramsay’s life, Liesl (Liselotte Vitzlipiitzli) helps him learn to live in the here and now and to be responsible to himself. He meets her while she is managing the Eisengrim magic show. Dunstan is initially repulsed by her, thinking her "the ugliest human creature" he ever saw. Her comportment and demeanor are masculine, and she apparently has a sexual relationship with a lovely young woman in the troupe. Dunstan, while not a magician himself, is quite free with his advice on how to improve the show.
It is Liesl who makes him aware that he has voyeuristic, outsider tendencies and that these are harmful. It is her comment that gives the book its title. Liesl labels him the “Fifth Business,” which is a type of character in opera who is always the extra person in any set of matched pairs; he has no match.
Although Dunstan becomes comfortable talking with her about many aspects of his life, and she helps him move away from his long-standing guilt over the rock-throwing episode, it seems that his comfort stems from the fact of his absolute lack of attraction to her. Davies empowers her in part through her masculine persona and, related to that, her sexual aggression toward Dunstan. Because he thinks she is ugly, not only will he not consider having sex with her, but he even thinks her actions are diabolical. Later, after they know each other better, they do become involved sexually. He has apparently learned not to make up so many reasons not to get involved with people and to take what life offers him.