Depends on whose iTunes Store account the book/songs were bought on. My wife and I share one account (mine). When I buy an app, she can then go to iTunes and download it again. When I buy a song on my MacPro, she can then go to iTunes on her MBPro and see the song as well as add it to her iPhone. So far it has work flawlessly.
What I think you might be running into is you and your daughter have multiple iTunes Store accounts and if someone purchases a song/book/app, it can't be shared with another iTunes account. Just a guess.