Surely, there’s no problem with this common little word, no trap for the proofreader, copy-editor or author.
Well, you would think not. But experience of a lot of editorial and proofreading courses shows that many people feel a strong need to put an apostrophe before the s to make the word possessive. Some even want to put one after the s!
Hers can never have an apostrophe. It is a possessive word in itself. So be on the look out for authors who make this error. This mistake crops up regularly in hard copy books, e-books, websites and theses. So please be vigilant. Punctuation errors spoil a book and make the reader unconfident of the author’s ability. The apostrophe is a difficult little beast and has to be tamed.
By the way, just for a change, today’s word does not have a Latin origin. Her is Old English and comes from the word hire.