Helen
There is no need to feel guilty about how you feel, grief is an ordeal we all have to go through at some stage and each individual death affects us uniquely.
My grandad suffered horribly with his dememtia, he was so scared and completely lost in a horrible place in his mind that his death was a blessed release for him, but it didn't stop the grief I felt when he died.
I still mourned for the grandad I had lost, the AZ was a tiny part of his life, it didn't negate the lovely man he was until the last few years of his life.
Your Mum was still your Mum and nothing could ever take away the love you shared with her, no matter how the AZ had affected her.
She will always be in your heart and mind, hold onto the good memories, you were a wonderful daughter to her as you still are a wonderful daughter to your Dad.
Take good care of yourself.
Love and best wishes
Kathleen
xx