Lenore is a bad person, but she is much LESS of a bad person than the other vampires are. Lenore is the only one even pretending to treat Hector like a person. Even if she has basically made him into a pet, its much better to be the family dog than to be livestock and thats an upgrade that no one else was offering him.
And lets be honest here, Hector being someones slave was always how this was going to turn out for him. Not because vampires are evil, but because Hector is a fucking child. Lenore made it clear as day to him in their conversation: Hector is always going to be used and abused by others because he has no goddamn initiative of his own, so he is always going to be a pawn and never the player. Hector had freedom, and he fucked it up by throwing in his lot with people using and abusing him anyway.
Hector literally doesn't know how to run his own life. Someone was always going to make him into a tool for their own ends, as has happened to him twice before in the show already. Lenore, at least, is fucking giving him something in return.