I think the ending was exactly right for that book. We aren't supposed to know what happened because it doesn't really matter.. for whatever reason that part of Nicky's life matters at the time the book is written and I think if we knew what happened beyond that it would change the way we felt about the entire situation. Imagine how different you would feel if you knew the baby got back to Charlotte.. would you hate her? Love her more? I think it's a good ending because it leaves you asking the same questions that Nicky has to ask herself at the end of the book.