Why are people saying "River Flows in You" is Bella's Lullaby?

I love the song River Flows in You but, why are people saying it's Bella's Lullaby? Did Stephenie Meyer say it was or something. I think it is a much better song to fill the role of Bella's Lullaby. the one in the movie isn't just piano. Well, I just want to know if Stephenie Meyer thinks River Flows in you should be Bella's Lullaby and how this got started.