I'm sorry--Thank you--You're Welcome (?)

I accidentally stepped on her foot (not hard, so no meltdown was required).

AKA: "Oops, Mommy! My toes. Oops! You step on my toes."

Me: "Oh I'm sorry."

AKA: "Say, 'Sorry for your toes.'"

Me: "Sorry I stepped on your toes."

AKA: "Okay. Say you're welcome."

Me: (???)

AKA: "Say you're welcome, Mommy."

Me: "Okay, you're welcome."

AKA: "Thank you, Mommy."

Me: (???)