Mother vs. Mommy

Yesterday Helena and I were watching the Eloise Christmas movie (I was working, she was watching) and there is a scene when Eloise's beautiful mother comes in looking stunning. Helena gasps and says "I want a mother!" "You have a mother silly, I'm your mother." I respond looking up from the laptop. "No, you're mommy." She says with a "get-real" expression on her face. "Well, yes, I'm mommy too but that's the same thing as being your mother." "No it isn't." "No? What's the difference?" Helena looks at me with her head to the side considering this question and says finally: "You're my Mommy." End of discussion. I'm Mommy. Not "mother," not "mom," and not "mum." I'm her Mommy, period. That's all there is to it. And I'm fine with that!