Alli is a British pureblood of Jewish Polish descent. She is the only child of a single mother and grew up in a wizarding community north of London. She enrolled at Hogwarts School of Witchcraft and Wizardy in 1998 and was sorted into Slytherin. She does not get along with most of her housemates, and instead befriended Miranda Swan, Karen Dwimmer, Emma Mason and Jenny O'Meara. In their third year, the group expanded to include fellow Slytherin Vivian Sun.