Help with easy to use food

I have mentioned before that my mother has dementia. Up until now she has done really well with cooking her meals. They go on at the same time each day and are eaten at exactly the same time.

For some reason - possibly because she woke up early - she had put her lunch on (Wiltishire Farm Foods) at 10.30 this morning. She said it was because she was hungry having got up at 5.00 a.m. I am worried she didn't have breakfast and the carers are going to keep a diary for me having checked when they go in first thing but I know she is unlikely to let them help. I did think of putting a weeks breakfast (Cornflakes) in a see-through boxes so we could see if they had gone but I don't know if she would recognise them.

It would be difficult to convince her to let anyone help her with getting her meals and, to be honest, it gives her a sense of looking after herself so I don't want to interfere any more than I have to but I don't want her to be hungry either She has Yoghurt Corners in the fridge and similarly packed rice puddings which I can suggest she has at different times. She is very ridged with her routines - at one point she always had Heinz Tomato soup for lunch - but now it is WFF for lunch and WFF for dinner.

Has anyone any ideas about leaving something I can remind her about (or give her fairly quickly) that is easy to open and might fill a gap if she seems to have missed a meal. I will have to work out a way of someone else getting them for her eventually I know - I think we would have to disconnect the cooker because she has just gone on with her routine when she was ill in the past and doctor put extra carers in, but I am trying to work one step at a time.