<p>“it was you who let her go” is this grammatically correct?</p>
<p>and can you give me a couple of other examples, preferably some advanced ones to really let this concept sink in.</p>
<p>it was you is correct. it is the same as saying “this is she” on the telephone. “to be” is a linking verb; the nouns on either side of verb should be the same declension.</p>
<p>examples: she was my best friend whom i betrayed. “whom” is used as object, not subject. “i” is the subject.
i like the professor who taught the course. “who” is a subject: the professor teaching the course</p>
<p>so it is “it was you who let her go” and not “it was you whom let her go” ? what is the subject and object here then?</p>
<p>Yes that’s right, “her” is the object and “who” is the subject. See wg90210’s example, in which “whom” is the object. In these cases I usually try to rephrase the sentence, substituting an object for whom and a subject for who. For instance, instead of “she was my best friend whom I betrayed,” I would think “I betrayed her,” implying “whom.” “I betrayed she,” implying “who” is a more obvious mistake.</p>