Answer:
you nicely tell them in a private place, embarrassing them in public will make the situation not so comfortable and they will feel very self conscious. "I'm saying this cause I care" is not how you want to go about it because to them you will sound insincere. If she yells/talks back to you let her get her anger out because that is just a way to deal with the defensiveness but be clear about your concerns and have an open mind on a solution
