In Avatar Grace has a positive attitude and mindset towards the Navi people.
Then why does Eywa reject her body to the avatar?
In this site, you can read that (emphasys mine):
In a trance-like state, the Na'vi and Mo'at prayed in the hope that Eywa would permanently transfer Grace's consciousness to her avatar body. Unfortunately, she succumbed to her wound, but before she passed away, Grace told Jake that she was with Eywa.
So she actually died before the cerimony was complete, but her consciousness survived and lives now within Eywa.