姐的笑意你看不懂妹的悲伤你猜不透
[jiĕ de xiào yì nĭ kàn bù dŏng mèi de bēi shāng nĭ cāi bù tòu]
This nickname expresses complex emotions of a person who feels that they understand themselves deeply while others cannot truly grasp their feelings, especially the contrast between smiling and sorrow within family or relationships.