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 guess I should have caught on I mean, how clean can teeth get? My brother's going through that right now, he's such a mess. How did you get through it? Well, you might try accidentally breaking something valuable of hers, - say her... - ...leg? That's one way! Me, I- I went for the watch. (..)1994 TvShow: Friends Title: The One Where Monica Gets a Roommate Season: 1 Episode 1