I dont know why but I feel this is a bit different from wn, well might be because they change it in the ln or the manga rush it.
From what I remember, he separates her head from her body and maintain it with barrier magic so she wouldnt die, like, her head was actually connect with her body by barrier but it looks separated physically. And then she beg him to put her body and head back and apologize for what she has done to charlotte and his family. As a warning, he put the collar so the head won't fall and people won't know about it. And if she done it again, he will kill her for real
Yeah, she knows about him being her son
Correct me if I wrong because I read it a long time ago and use google translate
