Okay, I've been thinking and debating a lot about different situations and I think I finally settled on how Cinead might claim Anna. Let me know your thoughts.
When we finally get to the party, have them go off on their own and Cinead has to save Anna from the creature that attacks, i'll have him change back into his human shape before the kiss happens. When that does, he'll be surprised that she can still find him attractive even though she found out that he isn't human. He'll be so overcome and feel a rush of affection and a desire to keep her to himself that his magic will react, Forming a bond between them. I was thinking of maybe having some sort of marking appear on Anna, perhaps a flame of some sort. .. There are a few other details that I've considered, but I was wondering what you thought of just this starting point.