Who is Sudi from Sisters of Isis: The Summoning and what is their importance?

Sudi, the book's main character, is a teenage girl who lives in Washington, D.C. with her parents and younger twin sisters. She is a normal teen, consumed by friends, clothes, parties and boy problems, and she finds her sisters' fascination with magic to be a silly waste of time. She recently broke up with her boyfriend, Brian, when he began dating another girl, but she is not especially upset about it because she actually prefers a boy named Scott and she was disturbed by Brian's dark side and reckless behavior.

Sudi's normal life changes forever when she meets a young man named Abdel, who informs her that she is descended from ancient Egyptian pharaohs and, along with two other girls who are also Descendants, she must prevent the evil Cult of Anubis from turning the world into chaos. While she finds the story unbelievable and assumes it is a joke or the premise for a reality TV show, she soon undergoes a series of strange events, finds that she has the ability to transform herself into a bird, and learns to use spells and incantations to ward off danger. Sudi gradually accepts her newfound powers and although she is sad to think that her life has changed forever, she feels an obligation to protect her family and her world from the evil forces that are trying to destroy them and she learns that she possesses more power than she ever dreamed possible.