The protagonist lives in a village at the base of a mountain. Everyone in this village owns some kind of cat-like animal with the semi-magical power to take bad feelings away except the protagonist who is allergic. Getting water requires an arduous journey up the mountain to a reservoir, made more dangerous by the “wisps” (or maybe will-o-wisps?). The wisps are little balls of light that come out at night which everyone fears.
The protagonist follows one of the cat-like animals one day and discovers a graveyard where they go to die. She discovers that, when they die, they release wisps, which are like all the pent up bad feelings they’ve absorbed over their lives. While there she climbs some kind of knoll and I’m fuzzy on the details but something happens that results in her being bound in some way to a newly created wisp, which gives the wisp some sort of subtle influence over her and her emotional state.
The protagonist then has to journey home while bound to a wisp, which tries to do things like demoralize her and lead her off cliffs. She reaches the reservoir and the wisp manipulates her into jumping/falling in. She ends up sucked through an underground river and wakes up in a cave on the other side of her village. The wisp is there, but the connection it had to her is broken. So she’s discovered the reservoir is connected to and underground stream which runs near the village. She goes back with plans to tell her village about the river and ideas about to tap it for water.
Thank you in advance so much for your help, I’ve been trying and failing to find this book for 15 years!