Hello
If you're in the US, it appears the requirement is 13 years or older - "If you're less than 13 years old, Apple Pay isn't available and you can't add a card in the Wallet app. Age varies by country or region." Which you clearly meet.
Support Page - Set up Apple Pay - Apple Support
Could you verify your daughter's Apple ID reflects her correct age? You can learn how to update this here - Update the birth date associated with your Apple ID - Apple Support.
Any alerts / messages you receive when attempting to set this up would be extremely helpful!
I hope this helps!