Why is holo attracted to lawrence?

Because he is so good natured and she loves teasing him. Also he accepts her for who she is.

Idk mayb her wolf half imprinted on him

because that he accepts her for whom she is and she loves teasing him

To be honest, I feel that she is attracted to him because he is the only person around who knows her for what she is. The he really is the only contact she gets on a regular basis. The Anime and the Manga have already established that she is very lonely, and that will sometimes drive a person into the nearest open arms. No offense to Lawrence, but I feel if there was another male traveler with them, he would not be the target of her affections