Not, of course, to be confused with the American aviation pioneer who's been gone for over 60 years!

Aka Joanna (or Joanne) Ruth Nichols, she was born in Toronto. Her first novel was published when she was 18.

This was ALL I could find:

https://obituaries.thestar.com/obituary/ruth-nichols-1088686439
(with two comments)

"Joanne Ruth Nichols, age 75, celebrated Canadian author of young people's fantasy and adult historical fiction, died, on Thursday, August 11th, after a long illness. Her many novels included 'A Walkout of the World,' 'The Marrow of the World,' 'The Song on the Pearl,' 'The Left Handed Spirit,' and 'The Burning of the Rose.' Ruth was the daughter of Ted and Ruby Nichols; sister of Deborah Court and Rachael Nichols..."

https://www.thecanadianencyclopedia.ca/en/article/joanna-ruth-nichols

"Joanna Ruth Nichols, children's writer (b at Toronto 4 Mar 1948). In A Walk Out of the World (1969) and The Marrow of the World (1972), Nichols portrays the adventures of troubled children transported to alternate universes. The latter was Canadian Children's Book of the Year. In Ceremony of the Innocence (1969) an adolescent must resolve conflicting feelings towards her father. Song of the Pearl (1976) treats the moral growth of Margaret, who, after her death, examines her behaviour in earlier incarnations, while The Left-Handed Spirit (1978) recounts the young heroine's discovery of her special healing powers. The Burning of the Rose (1989) is an adult romance set in Renaissance Italy and France.

"In all her novels, Nichols traces the difficult quest to attain self-knowledge."

https://www.google.com/search?sca_esv=586071440&q=ruth+nichols+books&tbm=isch&source=lnms&sa=X&ved=2ahUKEwjm5OGc0-eCAxWklIkEHUaZAXIQ0pQJegQICRAB&biw=1920&bih=884&dpr=1
(book covers)

https://www.google.com/search?q=++ruth+nichols+kirkus&sca_esv=586071440&ei=EF1mZeTtBb6lptQPlamKmAw&ved=0ahUKEwjktZuM0-eCAxW-kokEHZWUAsMQ4dUDCBA&uact=5&oq=++ruth+nichols+kirkus&gs_lp=Egxnd3Mtd2l6LXNlcnAiFSAgcnV0aCBuaWNob2xzIGtpcmt1czIFECEYoAFI0xdQd1jqFXABeACQAQCYAYABoAHvBaoBAzguMbgBA8gBAPgBAcICChAuGIAEGIoFGEPCAgsQABiABBiKBRiRAsICBRAuGIAEwgIFEAAYgATCAgYQABgHGB7CAhkQLhiABBiKBRhDGJcFGNwEGN4EGOAE2AEBwgILEAAYgAQYigUYhgPCAgUQIRirAuIDBBgBIEGIBgG6BgYIARABGBQ&sclient=gws-wiz-serp
(Kirkus reviews)

https://www.goodreads.com/author/show/5847641.Ruth_Nichols
(with photo)

She had one entry in the "Something About the Author" encyclopedia series and an entry in volume 149 of the "Children's Literature Review" series.

WORKS
Publications for ChildrenFiction

A Walk Out of the World, illustrated by Trina Schart Hyman. Toronto, Longman, and New York, Harcourt Brace, 1969 .
The Marrow of the World, illustrated by Trina Schart Hyman. Toronto, Macmillan, and New York, Atheneum, 1972 .
Song of the Pearl. Toronto, Macmillan, and New York, Atheneum, 1976 .
The Left-Handed Spirit. Toronto, Macmillan, and New York, Atheneum, 1978 .

Publications for Adults
Novels

Ceremony of Innocence. London, Faber, 1969 .
The Burning of the Rose. New York, St. Martin's Press, 1989 .
What Dangers Deep. Headline, 1992 .

Other

Framework for Reading, with Joan Dean. London, Evans, 1974 .