Do you throw out donated food?

Hi, I need an advice.

My grandmum loves cooking for her family. But she's almost 90 and doesn't really understand what veganism means. For example she thinks if there is no floating meat in a soup, only vegetable, it's vegan and doesn't understand that if she cooked it from bones/meat, it's not vegan. Or butter, she thinks if she only used butter during frying, it's still vegan.

She gives me food all the time to carry home. She cooks daily (she's home alone all day, doesn't go out anymore, so she cooks, bakes, reads books and do crosswords). She herself only eats a little bit and the rest is given to me. Few portions is eaten by my mum but I have to throw out the rest. I always feel so bad about it. I don't want to eat it but I feel terrible that I'm wasting food.

I work from home, so I can't donate it to someone at work. I also don't really have time to travel to some shelter, plus I think they wouldn't accept it because it might be poisoned.