Yes, i've seen her drinking but in very small amounts. I remember one of the live feeds showed her pouring half a glass of Prosecco and telling Tiffany that would be all she'd have so Tiffany was welcome to the rest of the bottle. I think it was when they were excluded from the Masquerade party.
i don't think alcohol was ever a specific issue for her, it was cocaine but as others have said many people in recovery from Drug addiction will try to avoid other potentially addictive substances as well.
I imagine with Alcohol and Drugs especially, it might be that if you become relaxed due to Alcohol, your defence and straight thinking might weaken so if somebody had some coke, yo_'d be more inclined to think "what the hell, i'll go for it".
Cigarettes don't change your actual thinking ability in quite the same way, although of course there are a lot of other issues health wise there.