User blog comment:Ygrain/Revisited: EDI and her purpose in the story/@comment-5287758-20121215162931/@comment-5287758-20121215165646

And for the merging to take place, the starbrat has to agree on allowing EDI to take its place. It singled out Shepard as the only organic ever to make it to the finished Crucible. I doubt the brat would approve of a synthetic to be responsible for the fate of the galaxy. And remember, only Shepard's "corporeal form" can be dissolved to get the desired control results. Too much space magic everywhere.