I'm not your mom

I missed a telephone call from my sister.  So naturally I called her back; my 6 year old niece answered the phone and this was our exchange.

Niece: Hello
Me: Hi
Niece: What are you doing?
Me: I'm returning a call to your mom.
Niece: Well, I'm not your mom!
Me: I know, I did say I was calling, "your mom"
Niece: Well I'll give the phone to my mom in one second.  Just like this, "one". Ok? Ready? One.
My Sister: (laughing) Hi... she's not my child...