Caroline didn't underestimate Jill. The chick had magic; she was no Bonnie Bennett, but she was halfway decent. Her water magic was...cute.
"Too bad," Caroline replied. "I was hoping she'd tap a vein for me. She's obviously a pro at it by now." Yes, you would have to be dumb not to know that Angeline was a prime source of blood for Jill. She figured Jill managed to get her fangs into a few others...maybe.