None of these things need cooking, or even reheating. I suspect that she can no longer remember how to use the microwave or oven, but just wants to take something out of the cupboard and eat it. The story about her not wanting fish pie etc because she "didnt buy it herself" sounds to me like a typical dementia "reason" to cover up the fact that she doesnt know what to do with it. If she goes out for a meal, she doesnt have to worry about cooking, so she will eat.Everything is sadly narrowed down to fruit salad (nice but too healthy) a thimball of wine, but now lots of chocolate and tonic water, and grapes.
Try buying things that are already cooked - mini pork pies, yoghurt, cake, biscuits, cherry tomatoes, mini quiche