I am having trouble attempting to recognise the grammaticality of the following syntactic contruction valid: "It's her alone who knows the truth". And is "it's her alone to know the truth" correct too?
A friend of mine in a letter wrote "it's she alone..." I remarked that "it's she" is incorrect. I find "it's her" to be more natural and more obviously grammatical, no?
Conservative grammarians maintain that 'It is her' is wrong as a copular verb shouldn't take an object. They have a theoretical point, but usage suggests that most either don't agree or couldn't care. I am afraid that different people will give different answers about its grammaticality. When the pronoun coming after the copular verb is also the subject of another verb, more will use the subject form, but most stick with the object.