couple of questions related to pronouns

Question

I'm reading "The Blue Book of Grammar and Punctuation", and there are some tests in the first chapter. There is this sentence, which needs to be corrected: That was Yusuf and me whom you saw.

The correct answers is: That was Yusuf and I whom you saw.

But why? I can't understand the reason.

I also have two other related questions: I was listening to a song and the lyrics were "no one hurts this pretty girl but her" Is her correct? Shouldn't it be a subject pronoun?

Another song related question. The title of a song is "The Devil in I". Is it correct or should it be "The Devil in Me"?

*both songs are by Slipknot, for anyone who is interested.

Thanks.

Answer 1

That was Yusuf and I / me [whom you saw].

Contrary to common belief, there is no rule of English that requires a nominative pronoun form like "I", "we", "they" etc., where the pronoun is complement of the verb "be". In the simpler That was Yusuf and me / I, nominative "I" would be ridiculously formal, and just about everyone would say "Yusuf and me".

Adding the relative clause "whom you saw" makes no difference: the usual pronoun would still be accusative "me", not "I". Additionally, "whom" is object of the verb "saw" in the relative clause, so one would expect an accusative pronoun here.

Answer 2

There are two ways to say this:

• Who you saw was Yusuf and I. (Yusuf and I was who you saw.) Nominative because Yusuf and I are not direct objects. They are a proper noun and a first person pronoun used as predicate nominatives.

• Whom you saw was Yusuf and me. To see someone, direct object. The basic form is: You saw Yusuf and me.

So, "That was Yusuf and I whom you saw" is a mistake.