I am sorry for you loss, and I am going to be blunt. You have, in your mind already lost your Gran when she began to suffer with Altzheimers. The lady you knew as your Gran went with the disease, leaving another lady who was not really your Gran. My own mother suffered this way for many years, and when she eventually passed I was sorry, but not distraught. I was like loosing a great great Auntie, a relative but not somebody that close, not like a mother. There is nothing wrong with you, I think you have already dealt with your Gran's loss. Loosing the actual human being is a less devastating loss.