[Wayne Luke]

If she is over the age of consent and not and underage minor, than its an issue between her and the provider of her internet. In this case her father. As far as I am aware, age of consent is 18 almost anywhere. Under that age, a child is under the auspices of their legal guardian and you should abide by the wishes of that guardian even if you disagree with them.

Since you're a parent reverse the roles. What if it was your child doing something you disagreed with and another adult said "It is okay, your father is just being overbearing." You would be furious if you're any kind of real parent.