Board Thread:General Discussion/@comment-4188031-20170221205101/@comment-4698889-20170221210329

I'm assuming you're basing this off of Triuberit's PV; please keep in mind that that PV is fanmade. All there is to describe the girl's life is that it's very unpleasant: "An unwanted life, an unwanted marriage"

That being said, it's quite plausible that Behemo's mother is the girl in the song, peering into a parallel world through the mirror. As for the implications of falling in love with someone who looks like you, I'll leave that up to everyone else.