RE: Kayla

The daughter, right? I don't think they ever explain the 'reason' we see her at the end. And why that guy has been here 'for a very long time'. You can surmise something but, unless I missed something, the explanation is missing.

I think she was a virgin sacrifice for the vampire prince teenager. That is what prolongs his life, she told him she was a virgin, and the past victims were also young women. Suggests a virgin sacrifice plot.