I am trying to find the name of a book I read as a child. The plot is basically that the girl who lives next door to the protagonist is weird and can 'float for joy' - that is, levitate. She turns out to be a descendant of Atlantis or something similar - an elder race in decline now living discretely amongst humans. They cannot interbreed - at one point the Atlanteans are described analogously to horses and humans akin to donkeys. The result is something like a mule. I think it might have been hazardous for the humans and the others to touch? Painful?
Media - Single Book / Novel
Date of Publication - Pretty sure it was in either a children's section of a public library or a school library and it pre-dates 1995. Might even pre-date 1988.
Major Themes - Decline of a race / empire?
Characters - Two children, one human, one otherwise. However, I cannot remember if the protagonist was male or female.
Language - The book was in English and I read it in England.
Target Audience - Older children? Teens?
Could this be Pilgrimage by Zenna Henderson? I loved this book as a teen, but I can only remember fuzzy details. Kind and good aliens are on earth, living among humans. The human protagonist is feeling hopeless at the start of the book and is rescued by these kind aliens. I do remember a passage in which the protagonist is shocked when she sees a girl levitate with joy.
I also thougth of The People, at the words Levitating with joy. Zenna Henderson’s stories is a good guess.
Except The People had children with humans.