Aaw Im really sorry to hear that mate. I think your dad was trying to protect you from it. Plus you probably have far better memories than her being in hospital with tubes poking out of her everywhere. The way I remeber my Grandad is unfortunately telling him Id see him later as he was sat on the edge of his bed he smiled, I walked off and that night he died. It is so hard not to remember them like that I would have preferred to not have seen him like that because it broke my heart. Your dad did you good in that or at least I feel he did. You may appreciate him for it later on. Death in any family is hard and it can hit one person in the family more than another.
Death hits a family on a whole and Im sure that people didnt mean to forget your birthday its just that something that hits you hard can knock you off balance if you know what I mean. Things in my family weren't right for a long time, my nan died then my grandad died and then my great auntie died within three months so we were all very unstable with it all. Remember the good times you had with her, for who she really was.
I hope everything runs smoothly for you. xxx