I want to say this is out of character, but she DID want to marry Fenrir after getting dicked once. So its pretty plausible that she'd fall in love with someone after a single conversation and night of sex. Though there is also the question of how she was a virgin when she first appeared if she's that easy to get into bed.
I remember when this series also had good story and not just the art: It was the first 2 chapters, then Reina got gangbanged by snakes and it was never the same.