It's a difficult one really...unless you'd been invited for dinner, you shouldn't really have expected it. I know the etiquette when I was a child (I'm 40 now) was unless you'd be invited to stay for dinner, you'd generally be expected to leave at dinner time. It sounds like you were there most days, so it was bit cheeky to expect to be catered for regularly and the likelihood is she wanted meal times to be just for her own family.
That being said, I can distinctly remember some "mean mums" from my own childhood. My best friend stayed with us most weekends...from Friday after school, to Sunday night. She had free days out to theme parks, free holidays with us etc. My parents would never accept any money for entrance fees or food etc, just said to bring some spending money for the gift shop and the likelihood is they'd also give her whatever they gave me pocket money wise to make us equal. We were friends from age 2-13, more like sisters, she stayed with us for over a week when her sibling was born again, no money given for expenses.
Her Mum took me out for the day, to the seaside, once in all those years. Two good wages in that family. I was 5, my pocket money was used to pay for my meal (sausage, beans and chips in a cheap arcade). Towards the end of the day, we went to an ice cream van. Friend's Mum bought two 99s (in the days when they were 99p). One for herself and one for my friend. She said, "I'm afraid you don't have any pocket money left so you can't have one, Perky." I sat beside them on the beach counting my pennies to see if I had enough to buy a Mini Milk...I had 12p and needed 15p. I'd gone back up to the van, excited as I knew I had 10p for one and that's how much they were at my local park only to find out they were 5p extra at the beach, so I looked a little deflated on my return. She told me to stop guilt tripping her by counting my pennies and to go off and play somewhere else so they could enjoy their ice creams in peace without having to look at my sulky face! I wasn't sulking, but I did feel a bit sad and confused because I'd never been in the position of being left out before and it was all a bit awkward as they were both really enjoying their ice cream and taking a lot of time eating it and talking about it while I was just sat there like a third wheel. And they were both sort of mocking me for not having one.
My Mum was furious afterwards and said she would have gave her the £1 on the doorstop on my return rather than treating me like that...she just couldn't understand a grown woman sat with her daughter both tucking into ice-creams and leaving a 5 year old out, then not even lending 3p so I could have something at least. She said she would have rather gone without herself than leave a child out. It was awkward as when I was collected my Mum asked us did we have a nice time and my best friend blurted out, "Yes we had Mr Whippies but Perky didn't have any money so she couldn't have one!" and laughed and my Mum said at the time, "oh, Anne, I'm sorry did I not send her with enough pocket money? Surely you know me by now and that I would have paid you back straight away if we'd owed any extra?" and then I somehow got told off by Anne for "having a big gob, telling tales to mummy". That was the last time I ever went out with best friend's mother!