It is important for you to show others that you care about them. It is important for you to say positive things about whatever someone does that you think will enhance their progress, their goals. This does not mean that one should not express any criticism, however, criticism done in an environment of trust where you have made it clear that there are also positives, is the most effective, and most loving way to make your point. Criticism should not be made without offering as well what you think can be done to help the person or the situation.
For example: If Mary wears clothes that you think do not enhance her natural assets, don't just tell her that you think she has no style or that you think she is tasteless. Why not go shopping with her and point out clothes you think would be good for her purchase. Suggest a 'pattern interrupt.' See if you can get Mary to go out with you in her new clothes so that she can experience how others might see her differently than before. Also tell Mary to watch this great video on UTube: send this link to any one you think needs it: