I genuinely don't know if IABU, so prepared to be flamed!
After services at our church, everyone sits down together for a cuppa, a biscuit and a natter. There's always fruit and often biscuits and milk available for the children. There's one woman who constantly goes against what parents say about what their children can have...for example a while ago, she asked my 2yo if she wanted milk. My 2yo is intolerant to milk, but says yes to most things offered. I intervened and said that she couldn't have it, but the woman gave her a cup of milk and said "but she wanted it". Then today, another child had just been told no more biscuits and she lent across and passed him one! And then, despite his dad saying he couldn't have tea, she gave him a cup of tea - "he wanted it"!!! We all sit round a fairly small table so it's not like she hasn't heard what's been said, she's deliberately going against it.
WIBU to be very loudly firm with her next time??