Was i wrong?

I live in a house with 9 people, in a 4 bedroom house. It's my in-laws in master, brother in law in one, another brother in law with his girl in another room, and us 4 people in one room, which was a 2nd living room but turned into a room for us. Ok so my family of 4 have only 1 income my SO, so we really aren't doing well but we aren't doing bad either, my SO works in construction so there isn't promised work for the the next day. Well yesterday we bought some groceries and some food to make my daughter's school lunch(she doesn't like the schools food) well since the income isn't really a stead amount each week we go for what we can, and I had the idea to put sticky notes on my daughter's school lunch things so no one else grabs them n end up having nothing for the week for her to take the lunch(no savings so we live check to check) just 6 things have sticky notes that say "Zulys school lunch" also my SO is ok with me doing this. So this morning I heard my mother in law say "oh so now we are naming things we buy so no one else gets them" our room is next to the kitchen ... so she did sound upset and I really don't feel bad because if no one buys groceries we could go the week with no food so we end up buying it. and when we buy groceries I can literally say they finish it before the week ends and we don't buy much due to income, also when my in laws buy groceries I really don't use the things they buy for reason. Mother in law will eventually say where is this or where is that and says it was for her or why did you eat it "playing around" but I know she isn't playing ... my father in law seemed bother a little but when I explain why he understood and was ok with it as well as my brother in law he understood. He was actually in shock my daughter takes lunch but understood and was ok about it. And mostly it's my mother in law that had a problem because of her son, he was the one that pointed it out, and since he is the baby and she is was to over protective of him she'll back him up in anything especially since he isn't all there he's at border line for mental illness...