Later be a stupid girl

We were watching end credit of a movie with a band & female front playing a song for a wedding.
Aresha danced away in the living room.
So I asked, "Do you want me to send you to a dance class?"

"No,"

"Why not? You can learn ballet..."

"Don't want! Later be a stupid girl!" complete with a grin.

Oh my! What has dancing got to do with being stupid?
Where did she get that idea?