If she causes them misfortune, you could simpy bind her from doing anyone any harm.
However if she just laughs at it, there isn't much you can do, and I don't think anything should be done, either. There aren't many effects of just laughing at someone.
There are mean spirited people in this world, but as long as they don't truly harm someone, it's better not to touch them. You can try to make her more positive, to bring a good change into her life in order to change her, but you can't be sure that it would work.
So I suggest you do your thing, she does hers, let it be.