There was a sci-fi book a book I saw about 10 years ago, that featured a society of people where (I think) some chose to become parts of spacecraft. I was very young at the time so i only remember fragments of the story.
There was a girl who was one of these people and was a part of a ship. These people could talk through the ship but were sort of a part of the engine. I think near the end of the book, the ship crashes and the captain tried to save her, but didn't know where in the ship she was located. I think she guided him to her but it was difficult for her to survive outside of the space craft, I do not know if she died or not.