It sounds like you and your friend don't have a clear understanding about how to share authority and responsibility in your business.My general belief is that one should not enter a business with a person who is a control freak or has an undying need to be credited as the fearless leader and source of all good ideas.One way to minimize the negative effects of such a personality is to have a written agreement that divides up responsibilities and authority, and prevents one person from dominating the important decisions that are made for the business.Even such an agreement might not stop your friend from acting badly--some people just can't help themselves.If she is damaging your interests in the business by her bad behavior, a written agreement can make it easier to make her pay...HOWEVER, keep in mind that this depends in part on whether your business has any demonstrable value.So, you can create legal documents but really still end up with a whole lot of grief and nothing meaningful that you can do about it.Some people need to feel like they are in control, and I would decide whether such a person can be manipulated easily enough (and my own ability to do so) prior to continuing in business. I would also ask myself whether I am content to quietly manipulate a glory-hound.