For the people who are confused, let me explain. So basically the white haired lady is the witch, not the girl who cuts heads off. The girlfriend was in the vicinity when she used her magic to slice everyone's head off then said "this is a problem", which means that they are now enemies. The white-haired witch returned and revived the two friends that got killed, which means she is most likely going to be on the male protagonist's side and there will probably be more witches besides the extremely crazy one who they will have to kill/defeat later in the story.
That last part was a theory but hey, you never know.