Should I tell my sister to being them food/snacks?

My sister has been bringing my two nieces over to my place since my mom takes care of them while they are on break from school. My mom rarely cooks unless they come over. I have a small pile of organic meat that I like to keep in my freezer but every time they come over she uses my food to cook for them. Should I ask my sister to bring them snacks and food? Does this sound mean to ask her to do so? She doesn’t buy organic meat and my mom uses my food to cook for them every time they come over and my nieces eat a lot. They go through the sour cream container so fast. Anyone been in this situation

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Should I tell my sister to being them food/snacks?
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