I think I would talk to your mother in the context of your husband. Tell her you have new house rules that *everyone* living or staying in the house must follow, and you need her agreement that she, too, will follow those rules.
This way it doesn't sound like a personal attack on her drinking/not drinking/hiding her drinking, while simultaneously letting her know that you have these boundaries that apply to *everyone*. (I'm assuming that you do apply those boundaries to all the people who come to visit you).
Seems easier to tell her that the boundaries were put in place due to your husband than to tell her it applies only to her (thus possibly triggering a defensive reaction).
As long as you make sure your boundaries (and the consequences of crossing those boundaries) are clearly delineated, it really doesn't matter so much how you get them across.