Hell yeah Mu Xiaoen <3
An interesting thing to observe is that strictly speaking, they weren't "losing" before she came, just being pushed around to quote Mu Xiaoen. The father was still facing pushback. And the argument "our Peachtown officer won't tolerate a kidnapping" works whether Mu Xiaoen is there or not.
What does change is that she's not hesitating or scared at all. Her presence turns an argument into a simple statement that the father has no place there and no authority. You can tell she's been prepared to face him.
As for the mother... good on her for finally doing something - late is better than never. Xiaoyang will only have spent an entire childhood without her support, yay ! Though the part that really sticks with me is that she was opposed sending Xiaoyang to conversion therapy even before coming. That would have been a point of no return even if she did change her mind afterwards.