Re:"I gave Toni Morrison her book back,"
the rule says pronouns refer back to nouns, not possive nouns that are considered adjectives.. so in the above sentence, her is refering to the closest noun (Toni Morrison) so it should be alright.
but "Toni Morrison's book was returned to her, today, by me." would not be correct, since her would be once again refering to the possive noun, Toni Morrison's which is really an adjective, since Book is the subject.
now one could argue that Toni Morrison's book is a subject phrase.. but still the subject is book and book can't be replaced by her! take out Toni Morrison's and replace it with a The
The book was returned to her, today, by me." and you have no idea who the her refers to.
