The Mansion of Black was definitely not a place to take a child. Putting aside the rumors about it being a haunted mansion, the decor was too child-unfriendly. Not to mention the intimidating guards and the few members of La Rose Noire who lived in the mansion. The girl would probably be scared to death.
Taking her back to her home was not a sane option either. After all, she had already taken her away, and the man had been punished under her orders. If she went back, who knew what he would do to her to vent her anger? She had investigated a little and found out that the man was a gambling addict—which was why they still lived in such an environment despite him getting large sums of money from his drug business.
Of course, she didn't think she had the right to judge him for being a drug trafficker since she was the leader of an underworld gang herself, which was not much better; it was just that dragging such an innocent child into it was nauseating.