When Zoolah's brother Mikah was supposedly found dead after guiding the Star of Deltora back to Del harbour, the Rosalyn Fleet took Zoolah in and made sure she wanted for nothing, as it was Mikah's last wish that Zoolah be cared for. 
Zoolah manages the running and organisation of the Rosalyn Trust competition. She is first seen admitting the candidates into the Traders' Hall for the examination. When she sees Britta arriving late she instantly does not like her, and finds her familiar, though she cannot think of why or how. She attempts to prevent Britta from entering the hall by claiming that the examination has already started and no more candidates can be admitted, but Britta objects and forces Zoolah to let her in. As Britta realises, this incident causes Zoolah to dislike her even more.
Zoolah is present during the examination as a supervisor. She is disappointed when Britta does not touch her paper before the writing time begins to put her out of the running. Later, when Mab sets the four finalists a second challenge, Zoolah is there to distribute the gold coins and shows a particular liking to Vashti. She further shows her suspicion and dislike of Britta and hopes that Britta will not pass Mab's test. However, it comes to pass that she does, much to Zoolah's annoyance. She accuses Britta of making an unfair trade (in other words, thieving) for the blue glazed candlestick she shows the traders, and refuses to believe Britta's claim that Sheevers is alive and gave her the candlestick.
After the test is over, Zoolah follows Britta from the Traders' Hall and back into the middle of Del, and discovers, as she already suspected, that Britta is not who she claimed to be. She harasses Britta, and again accuses her of cheating and thieving. Britta adamantly denies it. When Britta accuses Zoolah of attacking her in the alley, Zoolah appears to have no knowledge of what she is talking about. Zoolah threatens Britta's family, and marches Britta back to the Traders' Hall to reveal her 'deceit' to Mab. Lean Alice tries to stop her, but is unsuccessful.
At the Traders' Hall, Healer Kay turns Zoolah away, much to Zoolah's fury. However, Zoolah is not willing to back down quietly. After Sheevers arrives and accidentally speaks of Britta's true identity, Zoolah is furious and triumphant. She appears to be going insane, and is prepared to shout Britta's deceit so that everyone in the harbour will know of it. Just as she is about to do so, a freak wave caused by Britta's shadows floods the area near the Traders' Hall, killing her.
Zoolah is snobbish and high-minded. She is quick to judge Britta for her father's actions, and does not spare a kind thought for Britta and her family, referring to them as 'a mother who screeches like a fishwife and a sister who runs about the streets with her slippers, 'blubbering like a child'. Like most of Del, she is quick to judge and dismiss outsiders like Sky, Jewel and to an extent Britta. Because Vashti is a trader's daughter and of Del, Zoolah displays favouritism towards her, such as when she willingly allows Vashti to send a note home after the announcement of a second challenge, but then at seeing Britta's note voices suspicion and disapproval.
In the years after her brother's alleged death, Zoolah has become hateful and bitter, judging Dare's innocent family for his supposed crime and hating them for it, just because of their relationship to Dare. Zoolah is also very uncaring and heedless of other people's suffering and wellbeing, as seen when she lashes out at Lean Alice without a second thought and refers to her as 'vermin' and of no consequence just because of her lower class. It is also seen when she has the temerity to disturb Mab's much-needed rest in order to satisfy her pride and need for vengeance.
Zoolah cared deeply about her brother, and was devastated at his death. She grew increasingly bitter because of it, and came to hate the man she thought was Mikah's killer (and his family) with a vengeance.