I understand not believing it necessary to kill the higher vampire because they are not inherently dangerous, however, this wasn't just one higher vampire trying to get by. This vampire, unlike Regis, still drinks the blood of her clients, which, as she admits, acts as an intoxicant. Blood for vampires is just as disinhibiting as alcohol is for humans and can even cause such reckless behaviour as flying drunk. If this higher vampire and the higher vampires she makes out of the prostitutes are unwilling to refrain from drinking blood they are still potentially dangerous to the society into which they are attempting to integrate. Furthermore, Vereena, the bruxa from "A Grain of Truth," proves to be a danger to Nivellen despite her nature as a higher vampire and how she is not apparently intoxicated. Ultimately, I can't bring myself to trust an entire coven of potentially intoxicated higher vampires not to be a danger to society, so I killed them.
Sure, Patrick's a bit of a bastard, but he doesn't get what he wants. Besides, the familial dispute between the blue eyed lass and Patrick isn't really my problem.