SOLVED. Fantasy paperback, girl from underground society goes aboveground, befriends girl from tree society? [s]

[Sarah]

So I don't remember a lot about this book—not the title, author, author's gender, character names, nothing. I read it when I was maybe 12-ish, but I think it was an adult (written for adults, not adult content) fantasy paperback. I read it maybe in the late 90's, early 2000's, and I think it was older even then; I may even have found it in a thrift store. Maybe from the 70's, 80's? The cover MAY have had a girl with long, straight dark hair sort of bending over dramatically and maybe cuddling some kind of fluffy fantasy-type pet? But I may be confusing it with the cover of some other book :(

The plot had a (teenage?) girl who comes from an underground society—they live in like a cave system. She's forced to go aboveground (maybe due to food shortages? or a bad dude? or both?) I think she actually ran away, and maybe she took a small pet? She doesn't know what to do when she gets aboveground since she's never been there before, but then she accidentally meets a girl (pretty sure it was a girl, and like 92% sure there was no romantic involvement either way) who comes from a society that lives up in the trees in these graceful, airy tree city situations. The tree people think the underground people are monsters, I think, so they don't realize the underground girl IS an underground girl, since she looks pretty much like them (maybe paler and with darker hair?) The underground girl goes to stay with them, and for the life of me I can't remember what happens after that. I'd love to find this book for nostalgia's sake.

[Becca]

And All Between by Zilpha Keatley Snyder?

Eight-year-old Teera finds herself above the powerful Root that keeps her Erdling community captive underground. The Erdlings are feared and despised by the Kindar people who live in the massive trees above. Raamo and Neric, two young Kindar discover Teera and for reasons of their own decide to keep her hidden, allowing her to live with Raamo's parents and his sister, Pomma. But Teera's existence does not remain a secret and soon she, Raamo, Neric, and their friends are all in danger.

It was originally published in the 70s, but you might have read a 90s edition with this cover.

[Kris]

Note: Sarah (OP) was last active on the site in August 2019.

[Sarah]

That was it, you found it!!! Not a grown up book after all, huh. Maybe I was younger than I thought when I read it. Thank you!!!