Correct me if I'm wrong, but I think a prescheduled D&D session is more important than new plans with my grandma
Why is d&d more important than time with grandma?
Grandma is annoying and can not cook yummy food.
Playing d&d instead of spending time with your grandma isn't correct. Take the time to be with your grandma who loves you even if you don't like her food.
Maybe.
I think you'll be happy if you choose to go spend time with your grandma. Just think of how happy she'll be to have your company.