I am soo sorry to hear that you are going through this. The last paragraph you wrote had tears in my eyes...i FEEL the hurt that you're going through right now, even if I don't understand it.
We don't know...seems like such a cop-out, but in essence it's true. I don't know where your beautiful little granddaughter is in this universe other than her body is in the ground...but her life is with you. She lives through you and your family because of your love that you have for her and the memories you were gifted with from her time with you.
It may not be the "truth"...but hon, she's right with you.
I'm not sure if that's the answer...but it's all I've got right now.