I pretty much agree with Thumper, but then, you cannot force her into rehab. I agree the pregnancy is the stickie point. I was thinking along the lines of telling her that you will tell her doctor that she has been drinking and then the doctor will be the one to tell her that if she doesn't go to rehab, he will report her to the child welfare office. She won't like it one bit if they get involved.
Again, if it weren't for the pregnancy, I'd be suggesting you detach, go to al-anon (which you should do anyway) and figure out if this is really how you want to live the rest of your life. The baby throws a monkey-wrench in that idea though.