2Emily: I'll go with your initial statement that "In the case of "that is she" vs. "that is her," "that is she" would always be correct, but is never used." To me, "that is her" doesn't sound correct but I *will* & *do* use it because I hear it in conversational English in movies, books, songs. & that's what English teachers taught us in school. But it doesn't mean that anybody cannot question it & pay attention to, right? I'm just curious how this thing evolved historically. Maybe it's as simple as smb. once said "that's her/etc." & it went to the masses.
I have no problem at all with the question being asked. It's not the sort of topic everyone enjoys, but I do!↧