What to say to a cheating best friend

my bestfriend (20 female) has cheated on her boyfriend twice with the same guy. She started dating her boyfriend about 5-6 months ago and in that time frame slept with the same guy at 2 separate occasions. Her boyfriend lives far away and she has only met him in person once. She really is not a bad person, but i don’t know what to say. She feels horrible and i love her so i don’t want to bash her.