Go to counseling.
For what it's worth...I used to find ways to blur out all the feelings of "too much" while socializing. I'd go someplace quiet on the property or apartment or wherever we were visiting. A patio with plants, a corner chair out of the way, beside a bookshelf, under a tree. And just sit in the quietness. Or I'd pick a person to engage with and try my best to be fun or a good listener. Maybe she could try it? Also...try not to say things that make her feel worse about the social anxiety, while at the same time not reinforcing things that feed into some of the junk of social anxiety. So like don't say "Why can't you try harder?" type stuff, but DO hold her hand and lead her directly into situations sometimes where conversations will occur, and she won't be able to go drink. Hold her hand and give reassuring smiles that meet the eyes and rub/pat her shoulder and hand or arm a bit throughout, and make sure praise about something about her occurs. Then later tell her you're so proud of her and why. \\
So no one did that for me in that scenario, but it has been taught to me before and is worth a try.