Make sure you have a good doll on you so you can pacify the girl. When you see a friend being attacked by the girl quickly run over to her and either click on her or press the action button to interact with the girl but you need to be quick doing this. If you do this in time then it will give the girl a doll to pacify her and prevent her from turning your friend into a doll and attacking them and she will be calmed down and will walk around like normal and will unlock this achievement.