In Texas what age does a child have to be to decide if she continues visitation schedule with her father?

A child cannot legally decide to defy a court order. If there is some reason to not adhere to the schedule then go to court to modify it.

The custodial parent can be held in contempt of court if the schedule is not adhered to.

Agreed, a parent has a legal obligation to send the child for the ordred vistis, the parent can be held in contempt of court if they don't.

The child never has a "choice"

Now the child may testify in court and show a reason if there is a problem or danger with the visit. But it will have to go to court.