Turns out that at least six of her novels were juveniles, mainly about teens with disabilities.
An Open Mind, 1978.
"Torn by conflicting loyalties and emotions, a teen-age boy finally comes to terms with his father's pending remarriage with the help of a spastic boy." (The latter boy, Bruce, has cerebral palsy.)
A Time for Everything, 1979
"A young girl grows up amid many family problems in a small English village during World War II."
Only Love, 1980.
"When she finds herself the object of a young man's love, a spirited, physically handicapped 16-year-old is both touched and frightened for she knows she may now have to share her painful secret."
Sweet Frannie, 1981
"Paralysed from the waist down and confined to a wheelchair, Fran realises she hasn’t much of a future, but when she goes into Thornton Hall Residential Home, things begin to look up. For a start, she has a room of her own for the first time in her life. And pretty soon there’s someone else to think about: eighteen-year-old Luke Hawkins. After all, who better than fiercely independent Fran to help a young boy who has just lost both his legs in a road accident? A book of sweet and sour emotions that will bring tears of admiration and amusement as well as sadness."
Secret Places of the Stairs, 1984
"Seventeen-year-old Cass misunderstands her divorced parents until she discovers the secret they've been keeping from her: she has a severely handicapped, terminally ill younger sister."
No Time at All, 1994.
"Two disabled children love their new bungalow by the sea. It even has its own spectral steam-train which only they can hear each night. The train holds many mysteries which will change their lives."
From 2004, by Lois Keith:
"What Writers Did Next: Disability, Illness and Cure in books in the Second Half of the 20th Century"
https://dsq-sds.org/article/view/845/1020>
The article refers to Sallis' books, plus Jane Eyre, Little Women, Heidi, The Secret Garden, What Katy Did, Deenie (by Judy Blume), and Izzy Willy-Nilly (by Cynthia Voigt).