Answer:
If your thinking about creating a book, then create a scenorio and characters in your head and just let your mind expand on its own. Get ideas from other books, study different types of characters and personalites, and there's a bunch of websites too that can generate some ideas for you :)
A, it is informal. She is writing to somebody she personally knows, like her cousin, and doesn't mind if she gets a bad impression from it. Her cousin knows her well enough to not judge her.
I think its volume sorry if not