關於英文關係代名詞的問題。?

(1)In defining relative clauses the object pronoun whom is not used.You can use who as the subject of a verb. Hence who you're talking about=relative clause.
(2)In non-defining relative clauses whom is used and the pronoun cannot be left out.
eg:-I know the girl, whom you're talking about, has arrived.;
Hence I know the girl to whom you're talking about, has arrived.
cf:-The girl, to whom I known=whom 誰I known to=whom 誰used in formal writing, being the object form of who(who的受格)

句1 嚴格的文法得用
I know the girl whom you’re talking about.
我認識你談到的那個女孩

句2 文法錯誤, 若是要表達
我認識剛剛和你說話的那個女孩
得說 I know the girl whom you were talking with.

Amendment: That's the girl I knew you're talking about. Yip

1.I know the girl who you’re talking about.
我認識那個你在談論的女孩

2.I know the girl to whom you’re talking about.
我認識那個你正在跟她說話的女孩