I have to be honest. Much as I admire your friend for the improvements she's made in her life, which are very impressive, it doesn't sound to me as though she is anywhere close to being in control of her alcoholism.
I am the daughter, grand-daughter, sister and niece to alcoholics. I have known literally hundreds of alcoholics through AA, Al-Anon and other routes.
In my experience, while it's certainly possible for some alcoholics to learn to drink in moderation, it is vanishingly rare. The vast, vast majority have to stop drinking entirely. Many can't eat a pudding with 'raw' alcohol in, such as sherry trifle, safely. Some couldn't eat a stew made with alcohol, even though most of the alcohol has cooked off. Some can't even kiss their partners if their partners have had a drink earlier in the day. The fact your friend is still drinking at all is a red flag.
Another big red flag is that she uses alcohol to manage her stress. To the point of getting "properly drunk" - that's a third ref flag.
A fourth red flag, in the context of her drinking, is that other friends have felt the need to distance themselves from her. Presumably they're doing that for their self-protection.
I think that, however much of an immature, controlling arse her XH may be, his fears about her alcohol consumption are well-founded. I understand why he's reacting the way he does to her drinking (I'm not saying it's ideal, it's clearly not - but it is very understandable).
Her XH will have seen her at her very worst. You don't say how old her children are, but they may also have seen some awful things. One Christmas I saw my grandfather sobbing at the bottom of the stairs because he'd fallen down drunk and couldn't get his legs to work. I was terrified. As an adult, I saw my father wake up craving vodka, down a bottle, vomit into a bucket that he kept for that purpose next to his bed, and then drink the vomit because he was so desperate.
There is a (male) poster on here who had to tell his children that their mother drank herself to death. That's what the XH fears he will have to do for his children one day.
Your friend will have lied to her XH. Not once, but over and over and over and over again. She will have hidden her consumption from him. She may have hidden bottles around their house. Children's bedrooms are a popular choice for that (not saying your friend did, just that it wouldn't be a surprise if she did).
You blame the XH for not letting her back into 'his' house after her stint in hospital. I don't. Unless you've lived with an alcoholic you just can't comprehend what his life would have been like. Have a look at some of the threads in Relationships where posters describe their life with partners who are problem drinkers. They are advised - rightly - of the three C's: they didn't Cause their partner's alcoholism, they can't Control it, and they can't Cure it. And they are advised - rightly - that only the alcoholic can cure themselves and that they need to be away from the family while they do it. And that it will take months before they can be said to be 'safe' to come home, if ever.
Which brings me to what you can do for your friend. Absolutely nothing. All you can do is be there when (I'd like to say if, but based on what you've written I fear it will be when) she lapses.
You sound like a really lovely, good, person.