How WONDERFUL!! What a blessing she must be!! I would very much have loved to have more time with my grandparents - all of them. Wish her a very happy birthday from me!! And take her to splurge on her favorite whatever.
One year I was visiting my grandma alone on her birthday. We went out to eat at a fancy restaurant and for dinner she had a scoop of ice cream with green creme de menthe on top. She shared it with me (I was a teenager at the time) and it was a special thing just between us. I have cherished that and other memories of her for years. I cannot see anything with green creme de menthe with-o thinking of her and that day.
As a special gift, please please please please please take a voice recorder or video camera with you and get her to tell the old family stories to you, and her memoreis of childhood, family, etc... You will treasure them for decades. We have some recordings of my grandparents on each side telling the stories and they are among our prized possessions. they truly are a memory for you, a snapshot of her life, and unless you have them you will always regret not having recorded the stories.