FairyDust, this is certainly not a trend you want to continue.
If your MIL finds Christmas generally difficult, sad, etc then she needs to make room to express those feelings on another day and at another time on any of the other 300+ days, just not Christmas.
If Christmas spent at home is what you want, surrounded by those whom you wish to keep the company of, that's what you should have. Why should you have to go away and at extra cost?
You'll feel anxious if she's there, and likely uncomfortable with the idea of her absence, however, a calm Christmas is what you're aiming for.
As awkward as it is, it's not going to go away and needs to be discussed as soon as possible with your husband.
Your MIL could compromise and attend on the agreement that she has alcohol free wine/drinks...afterall, it's about the taste, right? If she's insisting on drinking regular wine, then that's where the line must be drawn. Added, that if she doesn't stick to alcohol free, then should be asked to leave and her invitation withdrawn from future occasions.
Same if she turns up/is picked up and she's already half cut.
Based on historical proof, your MIL can't be trusted not to ruin the occasion. Furthermore, feelings aside, extending an open invitation to your MIL and anxiously awaiting her attendance is likely setting yourself (and those around you) up for disappointment and anguish. It's not an occasion to be made about her, but unfortunately it's already becoming that - constructed around her. I know because I, well the entire family, had the same thing for 2 decades with my MIL.
I'm not one for alcoholism being a disease (it's the pattern of unaddresssed underlying trauma, grief and disatisfaction not the booze) and to excuse someone for poor behaviour (as my husband and his family did) is enabling - the drunk don't eat %hit! Christmas day is no place to make room for one person's dysfunction, why should you and everyone else keep putting yourselves aside to accommodate one person's toxicity, MIL or not?
I fought my own husband and inlaws for the same thing. Nothing changed.
We're now divorcing, have an adult child and only after many ruined Christmases, Birthdays, you name it, always special occasions, which can't be replaced. It didn't happen because of my MIL's behaviour alone, but because the family made room for it, repeatedly. And she still hasn't sought help, because she lives in denial, blames others, is unappreciative and never remorseful.
Though undiagnosed it appears, my MIL is Borderline and rather Narcissistic, neither can be fixed.
The solution for my husband and family in law all these years has been to hide the wine, put up with her rants and abuse only to be asked to smile the next day and not hold the MIL accountable for her behaviour. No consequence, no need to change.
So, not in so many words, but the message received was that everyone else must accept her as she is, and everyone else, but her must make changes infinitely.
It's such a difficult thing, but if things remain the same, everyone loses...
Wishing you the best x