Call your friend out in private before you call them out in public. One builds them up, one burns them down.

In public, the audience changes what the conversation is even about. Your friend stops hearing the point and starts managing how they look, so the thing you wanted to say never actually arrives. In private, the same words are just a friend telling them something. Identical content, opposite effect.

If something needs saying this week, find the walk home, the empty locker room, the car. Start by making clear you are on their side, and mean it. Save the public version for compliments, which work better with witnesses anyway.