hi
@thalia welcome to TP
I hope the carer arrangements fall into place soon as it's a lot for you and your sister to take on yourselves
as one of you is visiting each day, might you clear the house of food stuffs so that your mum can't actually get hold of the makings for meals - she may well be not realising that she has already eaten, and/or is making meals as a habit; it's one of the things most women have done every day almost all their lives, so she 'knows' to go through the motions but is losing the rationale behind having 3 meals a day
with my dad I used to leave a banana and the makings for his breakfast all ready on the table (OK as long as he could remember the milk in the fridge) - some made up sandwiches, cut up fruit, an individual yogurt/sweet, a biscuit and a carton drink for his lunch - with a bowl of packet mini-cakes or treats of various kinds and a jug of squash left out for him to graze if he wished - then a ready meal for his main meal so it could be microwaved by him (then me when he couldn't remember how) - in effect, there were no inedible foods left around - and I had everything in small portions eg the sandwich cut into fours, so any one thing was only a few mouthfulls
I had some tinned stuff in a cupboard for emergencies and frozen ready meals, bread, ice cream etc, in the freezer, which were safe as he didn't go in the cupboards or look in the freezer - and there were bottles of squash, tea coffee, milk in the fridge for hot drinks
sometimes I did make meals from fresh for dad, and even got him to help me, but I brought the ingredients with me
and he did eat better when I sat and had the meal with him, especially as he 'progressed', as he would watch what I did eg with the cutlery and copy me, and because I was there he was much less likely to wander off mid meal (his favourite habit was to need the loo mid meal and then go into the living room and settle to watch TV rather than realise he had a half eaten meal waiting in the kitchen)