The Haunting of Charity Delafield, by Ian Beck. I have en-bolded the things that made me want it!
"A magical, enchanting tale, with stunning illustrations that will transport you into another world.
Flame-haired Charity Delafield has grown up in a vast, isolated house - most of which she is forbidden to explore - with her fiercely strict father. With only her kindly nurse, Rose, and her cat Mr Tompkins for company, she knows very little of the outside world - or of her own family's shadowy past. What she does know is that she is NEVER to go outside unsupervised. And she is NEVER to over-excite herself, because of the mysterious 'condition' that she has been told she suffers from.
But Charity has a secret. All her life, she has had the same strange dream - a dream of a dark corridor, hidden somewhere in the house. Then, one day, Charity stumbles across the corridor. It leads to a door . . . and suddenly she realises things are not quite what they seem."
Sounds good, yes? I realize that wanting a book because it has a "flame-haired" main character is a bit shallow, but there it is. Especially after reading Marion Zimmer Bradley's Darkover books, I have wanted to be flame-haired myself....or at least burnished chestnut...