I think you made a very wise decision. I hope you see how that after you spoke with her and made it very clear, she just had to text and ask again. And, then she makes it about her and what she wants to do (add guilt). I hope she will respect your wishes and not show up.
This decision shows a lot of strength, Chris. If you continue to be independent of her control, you will be able to spot her manipulation and selfishness more easily.
I'll be thinking of you and your family. Grandmothers are a blessing to our lives.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!