Hmm, if I had to choose only one, it would be Jean-Claude. He's there for her, he quite obviously cares for her, and while he is selfish and has many ulterior motives, he doesn't really hide that aspect of himself. Also, he is better able to protect her than someone more easily killed, because he is a vampire and the Master of the City. All around I think he would be the best if she could only have one (though I would feel sad for Requiem).