Thank you Mlynn and GingerM. Well, I talked to her friend who was there visiting a couple weeks ago, and she IS drinking again. In fact, when he got to the airport, she told him over the phone that she had had too many, and couldn't pick him up.
I know I need to confront her, and lay down the law, but I hate having to do it, because she can get incredibly mean and nasty when she is "cornered."
I don't want to tell her about my boundaries with my husband, because she has always hated him, and I'm not giving her any more ammo. I pretty much keep my personal business with my friends and husband to myself. She would not be staying with us anyway, she always gets a hotel when she is in town.
I don't want to get her friend in trouble by letting her know he told me about the drinking, I think I will just plain out ask her, and tell her her behavior has made me suspicious, which it has.
What I need to decide is, do I even see her, or tell her that I refuse to see her until she gets herself back into treatment?