She cannot make business decisions in her will; what she can do is decide what will be done with her share(s) of the company. For example, you say it is a corporation; say that there are 300 shares of stock, and each of you, the husband, and the wife own 100 shares. She can indicate who will get her 100 shares, which may give one person or majority, or else bring another person into ownership and management. But again, all wills do is dispose of property; people cannot manage "from beyond the grave" by them, except indirectly, through the person who gets any stock or other ownership interest.If she is adjudicated incompentent, then she would not be able to make business decisions; but without a court determination of incompetency, she may still manage.