Beale was one of six children of a dairy farmer Cedric Corney and of a teacher and author Estelle Corney (née Cook). She was born in Inglewood, Taranaki, New Zealand, on the farm where her father was born. Beale grew up in the town before attending Victoria University, Wellington and Christchurch Teachers' Training College, where she met her husband. Since 1985 she has taught at Melville High School in Hamilton, Waikato and in Wellington. Beale's first stories were written for the children's radio programme Grandpa's Place. Her first book was a small reader and picture book for young children and she started to write for teenagers in 1993. Her stories often involve troubled adolescents engaged in outdoor activities.

Beale was a finalist in the Aim Children's Book Awards (junior fiction) and her 1998 novel I am not Esther was shortlisted for the senior fiction section of the 1999 New Zealand Post Children's Awards. In 1999 she was awarded the Children's Writing Fellowship at Dunedin College of Education and quit teaching to write full time. Her 2001 novel Ambushed was a finalist for the Junior Fiction section of the 2002 New Zealand Post Children's Book Awards. Her 2004 account of how an indigenous girl discovers how her education can save her tribal lands (My Story A New Song in the Land. The Writings of Atapo, Pahia, c.1840) received a Notable Book award in 2005 as did Walking Lightly.

Fourteen-year-old Kirby Greenland's mother leaves her with unfamiliar relatives in a strange city, supposedly leaving New Zealand for two years to help refugees. Kirby's new guardians and their six children belong to a strict fundamentalist Christian sect called the Children of the Faith. They abhor all recreation and any immodesty, devoting themselves to industry and bible study. They insist that Kirby must leave her old self behind and emphasise that Kirby dissent, her uncle insists that the entire family prays over her until she repents. Concern for her youngest cousin prompts her to relent but she soon becomes aware that she is losing her identity and determines to escape although she feels responsible for the cousins that she has grown to love. She is also concerned about the fate of her cousin, Miriam, who disappeared shortly before her arrival, but is barely mentioned by the family, other than her being "dead". She knows that not all the children of the cult members are completely indoctrinated: her cousin Daniel wants to be a doctor, despite the proscription on higher education, and her schoolfriends misbehave when they are away from home. Kirby and Daniel are thrown out of the sect at the end of the book because he reveals his wish to be a doctor "so I can help you all". A mass brawl/fight scene ensues as the Elders (leaders of the faith) beat Daniel black and blue (literally). They go to Wellington, and find Kirby's mother in a psychiatric hospital and help her to recover. Meanwhile Kirby has been having nightmares about becoming Esther again; it is only when she sees a documentary about the faith that she realises "Esther is dead".

The title I am not Esther comes from Kirby's catchphrase "I am not Esther", as this is what her aunt, uncle and other people in the faith insist on calling her. She is worried that she is turning into Esther particularly when it is pointed out to her that Kirby would have said "I'm not Esther" ... the faith did not use abbreviated words.

Beale was inspired to write this by "a boy I heard about who had been thrown out of his family because he wanted to be a doctor". She describes the cultists with respect; she is hostile to the behaviour and not the people. Despite this, the cultists are depicted as brutal opponents of the brave doubters, largely as a consequence of using Kirby's perspective.