emptyworld: Welcome to SR. You have come to a very supportive place.
I too am from Michigan. But i do not know the laws here as far as what steps your family can take to get your sister into treatment.
As scared as you are for your sister that something has to be done NOW to help her, the best thing you can do for your sister today is to commit yourself to your own recovery program (namely Alanon which is a 12-step program for the friends and family of alcoholics). Also reading the stickies at the top of this. Also independent reading. There are tons of good books out there on alcoholism and the effects on the family. At some point you may be able to talk to an addiction counselor about how to help your sister (as in an intervention), but that requires several family members who are all on the same page about how to help your sister - which namely involves the willingness to stop enabling your sister.
Please remember that you did not cause this, you cannot control this, and you cannot cure it. But you do have a Higher Power who is working on your behalf and on behalf of your sister.
Others will come along with good wisdom for you. Hang in there. Keep coming back.