How to kindly tell someone (who's not your friend) to shut up?

Well if she really is that insensitive, why no confront her about and tell her that what she says really hurts people, and that she should be more considerate of other people's feelings. I know a person like that as well and i does get annoying, so i think that you should tell her exactly what her problem is and tell her to stop. I really hope this helps!