I am an only child in the family, and I have always wanted a big sister to look up to. One day I met Amy and made friends with her. Ever since then she's like a sister to me.
 like a sister to me surrogate sister godsister英語中沒有乾姊姊或乾妹妹的說法, 所以白話翻譯. like a sister to me 是最常用的.