It was DS2's christening last week and like the gluttons for punishment we are, we had the lunch reception for 30 at our house.
My GM couldn't attend and told us she was too unwell weeks in advance ( I suspect the real reason was that she can't be bothered as she was perfectly able to go out for lunch, go shopping etc the week before) but I accepted it as I have no idea what it's like to be older, I didn't want to upset her and it's none of my business what she does. She told us this weeks in advance and that's fine so I carried on with looking after my baby and toddler and organising the event. (I will never be having this size event in my house ever again it was so stressful!). The event was a busy and stressful success.
DM comes to my house to visit the week after and crossly says that GM was 'extremely upset' because I didn't save her some christening cake. It didn't even cross my mind, I was so caught up in it. I said to DM (who is her 'carer' and therefore has GM more at the forefront of her mind than I do as I'm baby and toddler wrangling) that she could have if GM wanted some (she was sitting chatting to guests the whole time whilst I was serving tea and coffee and looking after children) and she shrieked that it wasn't her responsibility. She demanded I went and bought some 'special cake' for her to say sorry. 
. I've sent her a thank you letter for the money she gave DS.
AIBU that it's not mine either? I feel a bit U as she is my GM but I had no idea she wanted any and if it had even crossed my mind I would have. And why is such a fuss being made over a cake? On the other hand I'm feeling a bit annoyed at being shouted at over cake.