Picky,
Be very careful of any foods which are supposed to be diabetic foods or sweets, the sweetener used for these can give the consumer diarrhoea.
I have been type 2 diabetic for 15 years and have been advised by my diabetes specialist nurse to eat two or three Dextrose tablets if I get hypo, to bring my sugar level up, so I would imagine if it is just a sweet treat occasionally it would be OK for Grandma Picky to have a couple of those. They are available in three flavours:- lemon,orange and blackcurrant and are like Refreshers which we used to buy as kids.They are available at most chemist shops.
Best thing to do really is for her to discuss what she can have with her diabetes nurse as we all vary and so do the nurses opinions.
As a general rule we are told that we can eat what everyone else eats as long as we don't overdo it and follow a sensible diet.I would imagine she has been told this.
Hope this helps.
masterchef