I read a book as a young girl and the little girl in the book’s parents are divorcing or some similar childhood trauma. She has a red backpack (not illustrated). She notices on the ceiling some snails and somehow (?) is turned upside down and finds herself on the ceiling with some little trolls that ride snails and they’re cold! to touch. She is kidnapped. She also meet some good elves/gnomes? The plot is around Jack Frost coming to freeze the pipes and flood the house but the nasty trolls are cutting the insulation from around the pipes and Jack Frost is a big scary entity. Any idea??