Identify what aspects of your sibling's behavior you find unacceptable. To do this, you'll need to observe her in a more objective way than you might normally. Set aside the fact that you love and care for your sibling, and focus on setting boundaries as part of her recovery process. The article "How to Set Healthy Boundaries with Addicts and Alcoholics," for the CARF-accredited drug rehabilitation center Promises, recommends writing down your sibling's behaviors over the course of a week or a month. Whether she is verbally or physically abusive toward you or other family members, consistently fails to stick to arrangements, or makes a spectacle of herself in public, recording all instances of such behavior is the first step toward establishing appropriate boundaries.

Decide on the consequences of your sibling crossing your boundaries. It's not enough to simply point out to him when he has done so, says Promises. Boundaries without consequences are pointless, because there is nothing to motivate your sibling to realize how his behavior is affecting your life. You may want to give your sibling details of your boundaries -- and the consequences of crossing them -- in a letter or email, suggests family substance abuse counselor Carole Bennett, M.A. in the article "Setting Your Boundaries," for "Psychology Today." Your communication should be as loving and neutral as possible, but make your position clear, advises Bennett.

Stick to your boundaries, even if this means separation from your sibling. Having strong boundaries is the healthiest way forward for both of you, says Promises. When it comes to an alcoholic relative, it is often necessary to be cruel to be kind. The more your sibling is made aware that those who care about her will not tolerate her behavior, the more likely she is to accept responsibility for her actions and seek the help she needs to turn her life around.