She talked about the past and you bring your majic ball to see future? The matter was between her father and mother.
You don’t even know what Stockholm syndrome means by the way. Useless addition of words there!
She (OP) is happy. That is what should matter. If you or anyone has sympathy for her mother then go ahead report her that her daughter is happy. No mother would want to see her daughter unhappy at her expense.
No she does not have to defend her father. You are just being judgmental and ruthless for no reason. Try not to bring something emotional or as if you know her mother better for sure.