Help: Book Wanted

I'm trying to find a book I once read and would be grateful for any help.

It's a book for kids or young adults that was probably published prior to 1990. I don't know the title, author, or any of the characters' names. A search for keywords on various book websites has turned up nothing.

The main character is a young girl who moves out of her family's house and into a structure in the woods. I think it was a small windmill, but it might have just been a tower. She wasn't running away, just sort of packed up some things and said she'd be living in the tower for a while.

She has fun cooking her own meals in the tiny kitchen and keeping everything tidy. The only part that really stands out to me is a scene in which a mouse gets trapped in a bottle. The girl had left an empty soda bottle in the sink and a mouse crawled in to get at the last drops of soda. The mouse is stuck and when the girl sees this, she's very concerned and tries to free it. She realizes that breaking the bottle would hurt the mouse, so I think she ended up figuring out some other way to release it.

I don't think I finished reading the book, but the concept of running away without running away has always stuck with me. I've found echoes of it in Virginia Woolf and other works of art in which women set themselves apart for their own reasons.

So if anyone knows what book I'm talking about, please let me know.

1/8/14 Update: I'm still trying to find this book. I've searched online again and come up with nothing. Help!