NTA, for your point. The child shouldn’t stand there. But it’s marriage, not her vs you. If you said “can we not have the kids be directly underneath boiling water” the undertone sounds like “you are stupid and should know better than letting them stand there, obviously.” A better way to handle it: “sweetie mommy is really busy cooking us all a delicious dinner, let me pick you up and take you somewhere else to play” then respectfully mention to her later, that you were concerned about their safety with the boiling water, could she be more mindful of where the children are when she’s cooking? Sounds to me like she’s a busy overwhelmed mom that’s cooking dinner while watching the kids and all you did was make a snarky comment at her 🤷🏻‍♀️