Britta sees Vashti during the Rosalyn Trust competition and views her as a snobbish, spoilt young woman, disdainful toward those around her. Most of the other candidates dislike her, but know that she will most likely become a finalist and set sail on board the Star of Deltora. In the initial testing of the Rosalyn Trust competition, Vashti receives an interview and later is announced as a finalist. Because Vashti, Jewel, Sky and Britta all scored evenly in their interviews, they were set an additional test by Mab and given one gold coin each to trade with in Del, and the most valuable item would win. Before going on the test, however, Vashti wrote a note for her parents where she claimed that "calm and firmness" would make her succeed. This was a code to let them know that she would use the shop Carme & Furness to win. During the additional test Mab sets Jewel, Sky, Vashti and Britta, Vashti does well, trading her gold coin for a splendid carved leather belt from Carme & Furness worth three gold pieces. Vashti, along with Jewel, Britta and Sky, sets sail on board the Star of Deltora at dawn.
Vashti is spoiled and disdainful, particularly towards others such as Jewel and Britta, and appears to share the prejudice most of Del feel toward outsiders. She is intelligent and able to spell and solve math and other puzzles, and snubs other people who cannot do what she can do.
The name "Vashti" is Persian and means "goodness" or "beautiful". It is likely a reference to Queen Vashti, a figure in the Jewish and Christian faith who appear in the "Book of Esther", the third section of the Tanakh (the Hebrew Bible). Vashti was the queen of Persia and the wife of King Ahasuerus. One day she refused to dance naked in front of him and was banished. Another woman, Esther, became Ahasuerus' wife and queen. In the Midrash, the the genre of rabbinic literature which contains early interpretations and commentaries on the Written Torah and Oral Torah, Vashti is described as "wicked and vain", but she has become a hero and icon in feminist versions of the tale.