The book is 'hers'. [=the book belongs to her; it is her book]
a former professor 'of hers' [=one of her former professors]
That face 'of hers' [=her face] is hard to forget.
(..) I went up to my girlfriend. I said, "You know, I'd like a little pussy." She said, "Me, too. Mine's as big as a house." You see, she wanted a littler one cos hers was... big as a house. Get that stinkin' shit out of my face. Bunch of slack-jawed faggots around here. This stuff'll make you (..)1987 Predator