Here is general guidelines from the book Ethical and Fair practices in Business. In summary: If you are: (1) a boss: (i) FIRE him, when you will use that fire-extinguisher. Its your golden opportunity to check out your fire-preparedness. (ii) Fire HER, when you will use that FIRE-EXTINGUISHER. Its your GOLDEN opportunity to CHECK OUT your fire-preparedness. (2) a manager: (i) USE him for Personnel management. Use suspension THREAT. (ii) Use HER for personnel management. Use SUSPENSION threat. (3) At the same hierarchy: (i) Ask him why I should take the extra-overlaod? Ask him. (ii) Ask HER why I should take the EXTRA-OVERLOAD? Ask HER. (4) If you don`t find any of these suggestions from the book Ethical and Fair practices in Business of your interest then I recommend you please read the book My experiments with truth by someone. I am sorry I have forgotten the authors name. You will find it difficult to get the book, for it is out of print since decades. Good luck Gentleman and good luck lady. I mean your lady luck will smile at you too. You will know yourself why? Just remember you will be making the negative coworker more dominant if you don`t do a frank talk. It may happen that it is your family business and the person in question is your fair lady. Don`t expect any changes. Criticism is part of their attitude. Consider yourself lucky that you are still able to work along with her for so long to judge ger as negative coworker. I appreciate your knowledge of judgement. How many years it took to realise this? Many people simply don`t know for the whole life.