There are always exceptions (which is why we have judges and courts of law, and this situation may very well be considered such an exception by whatever court rules on it) but, generally speaking, parents are responsible for negotiating contracts on behalf of their children, acting in their child's best interests. Children cannot enter into legal agreements on their own, so someone has to be responsible.
I am not going to argue opinions but if you are trying to state that children have a legal right to know their parents' identities, then you should be aware that that is very much disputed all across the country with no unanimous verdict one way or the other.
Because she and her mother accepted a large amount of money in exchange for forgoing that ability. Working against her is the fact that she continued to accept such payments for 7 years as an adult.