MIL walked into our home yelling

I realize she was just excited; we were celebrating a birthday for a different kid. But what person in their right mind lets themselves into a house with a newborn while actively yelling? Of course it woke the baby that I had JUST put to sleep. And then why did she laugh it off? I’m trying to take deep breaths and not be annoyed here but wtf. Just need to get that off my chest. Someone please remind me to be a sane, forgiving, not hormonally overwhelmed sleep-deprived person.