第一句: You are a good girl. 主系表结构. you是主语,are是系动词,a good girl则是表语. 第二句: You speak English very well. 主谓宾结构. you是主语,speak是谓语动词,English是宾语,而very well 则是宾语补足语.
"you" is the subject, "are" is the predicate, "a good girl" is the object. for the second sentence, "YOU" is subject, "SPEAK" is predicate, "ENGLISH" is object, and "VERY WELL" is object complement.