C-A-T

Today Bailee informed me that she could spell Dog and Cat... It went a little like this.

Me: How do you spell dog?

Bailee: "D-G-O...No wait...D-O-G"

Me: Ok spell Cat

Bailee: "C-A-T"

She's so smart. Should a barely 4 year old be able to do this? Somebody tell me.