Can't remember book title

I can’t remember the title of a book I read some years ago. It is about a young woman who carries around a baby seal, and she believes she is its natural birth mother. Does anyone know this book?

If you could put a tighter date range on when you read the book, it might help. Selkies have exploded in popularity over the last handful of years and there are hundreds of new novels about them.

It wasn’t really a selkie story. It was about a young woman in a community that everyone thought was deranged. I read it about 10 years ago.