Providing food for a family is expensive and the family shop is to be shared between everyone. If one family member eats more and there is none or little left for others that is not fair.
But getting angry about food is not good. Life is to short. Most of us are not starving.
My DGD and her cousin, my niece make cookies when they are over. My niece eats all that are left, despite my DGD and I telling her that they are for others.
Whenever she is over she goes to the kitchen helps herself to anything, doesn’t ask and finishes snacks.
My DGC do ask for things, my niece doesn’t. I have spoken to her mum, she says she does the same at home despite being spoken to.
The last time she was here, after she ate the last cookie left for DH, I told her quietly and calmly that she might consider others when she had had something before going to get another one. Let’s see how that goes.
I would not get angry with her though. She is 12 also.
In the heat of the moment maybe it can’t be helped. We have all eaten one too many cookies not thinking about others surely.
Talk to your DD about sharing. She won’t always be a child and these are important life lessons.