Could someone explain to me the point of introducing River as an echo in 7x13?

Since we saw her we knew how she dies & later we saw only her younger versions.
Other thing is that River's storyline painfully lacks consequence & logic, I think the handling of amazing & misterious character we met in "Silence is the Library" is really awful... But anyway - why suddenly make her ghost?! It's like taking away whole beauty & tragic of her "backward" journey with the Doctor. Or did I miss somethiing?