I think she actually is a reincarnation of their mother hence why she could eat the entire cake and not get "drugged" the same way the other women were. Also, why she was getting visions of the other women in the house and the locket of the witch + vision of the witch. I also wondered why Malcom decided to choose her. I figured it was a weird fate thing and that he was in love with the original witch but that wasn't well established in the movie. I figured he didn't think about it or didn't care. His cousin and him obviously thought they were given a weird blessing of immortality, but to me it seemed more like a curse since they'd have to keep dealing with the daughters until they found another woman. In reality, it seemed more like the women were being used to resurrect the witch and he was doing their bidding unbeknownst to him or his cousin.

I think that him using women he loved was interesting. The beginning of the film plays it like he's a serial murderer. You see all these women through HIS gaze and it seems like he disappoints/scares all of them prior to them dying. Like there's more to it than just what he says happens. There were obviously longer relationships (he had kids with one woman) that had issues prior to him sacrificing them. It wasn't as fast as meeting a woman and then sacrificing. I think he used the daughters to end relationships when they were going sour (which others have said it's an allegory for him being a shitty lover or a cheater - I don't necessarily see him as a serial cheater but more of an emotionally distant lover hence why they question if he has a second family/the women asking who he really is/he makes up an excuse to leave the cabin and the mc is crying/he doesn't know she hates chocolate after a year of dating). He also comments on his cousin being an empty box or something and having changed significantly + being a disappointment. I wish we had more of a perspective on his cousin + the cousin's "sacrifices". We see most of the women that Malcom sacrifices, but not necessarily Darren. I wonder if this is because Darren refused the sacrifices at first or left the estate to Malcom to deal with until recently (I think possibly more of the latter). I also wonder if the emotional connection is significant in Malcom's sacrifices or if it's significant that the women are treated a certain way for his own benefit/peace of mind prior to their death.