pronouns - can who be used as the informal form of whom?

In a grammar book, there were two examples used to clarify the difference
between who and whom, and to show that who can be used as the informal form
of whom, and there would be no difference in meaning. The examples were:

1. Bob is the young man whom she interviewed. (she interviewed whom/him)




2. Bob is the young man who she interviewed. (informal)

It's stated that the second sentence is informal, but our teacher insists
that in the second sentence Bob interviewed her (that is, the woman)!

Can anyone tell me which one is true? Is it just informal or does the
meaning change? Is the woman always the interviewer, or do the roles switch in the second sentence so that now he interviews her instead of vice versa?

Answer

Both sentences mean the same. The first is the sort of English used by purists, and the second is modern English, seen in daily usage.

Your teacher, without doubt, is wrong.