My point is: The OP didn't ask if it is okay to tell her daughter that the guy she married was her real father or not, and she definetly did not asked if her daughter need couselling or whatever advice you thought she wanted to handle not knowing who her real father is.
What is "Legal reality"? The court of public opinion? What law did she break? Yes mom lied to her child, so what? Do you have any idea why she did? Maybe you need to find that out why before calling someone a lier. I am sure she has her reason.
Yes, I agree. But I do know this. The courts try to do what best for the child. If they feel that this man took on the role of the "father", they will lean toward making him "father". And like I mention before the difference between claiming two children or three children might not be worth the effort. That is for the OP to decide.

