mdd: Are you asking because you don’t feel your wife dresses tzniusly enough?
Perhaps you can talk to her about it, and listen to her feelings, and empathize with her struggles and tell her you want to be the only one who sees her.
It would seem to be a lot more effective than “I’d like you to cover your shok, and tell your friends they should too, and if you don’t you are not following halacha and we don’t need to have sholom bayis anymore.”