This poor girl has been through the ringer.
Some family secrets are incredibly banal. It doesn’t affect your life that much to know that your mom had a fling with a cowboy in South Dakota during the summer of 81, or that your dad was engaged to a woman in Wisconsin that never came to fruition. It’s true that sometimes, your parents’ life is not your business, and you shouldn’t be snooping around to find out things that you don’t need to know about their past.
On the other hand, family secrets that concern the child shouldn’t be kept from them, especially regarding their parentage. It’s not right to hide that a child was adopted from them, even if it’s a difficult conversation to have. In ideal situations, it should never even be a conversation: the child should grow up knowing they’re adopted as a fact of life, no more shocking than finding out they have 10 fingers and 10 toes. But if you haven’t told your child who their biological parents are, the 2nd best time to tell them the truth is today.