If you meant that there is a certain age when a parent can still one-sidedly dictate whatever a child should do, then my answer is never.

Discussion and compromise will likely result in a better solution. If discussion is impossible (because the child is too young and immature) then it is slightly more complex, but it is obviously different in Asuna's case.

EDIT: Why the hell am I even defending Asuna. She can just die from ebola for all I care.