I think I would get out in front of it. Wait until tomorrow or the next day and call at a time you suspect she'll be sober. Tell her you value your friendship but you don't like being used as the designated driver so she can drink, and that you don't like to be around people who are drinking. Then request that she not call you anymore if she's been drinking, but if she's sober or wants to go to a meeting you'd be glad to accompany her.
I think if you wait then she's going to drunk dial you again and it could turn into a frustrated confrontation.
best of luck!
