It’s so hard to see our kiddos struggling! While not a “quick-fix”, if she wants to stay with that group, I would encourage her to find one person in the group that she might feel most comfortable with and arrange a time for them to meet up outside of dance. That way, she will have an anchor-person in the group to turn to for some level of comfort.
More immediately, I would recommend using lavender essential oil in a diffuser or on her clothing and a supplement like L-Theanine gummies by BrainMD 1 hour before a social gathering to calm the nervous system. It might also be helpful for her to find ways to increase her tolerance of anxiety with tools such as diaphragmatic breathing (belly breathing), and/or grounding exercises like noticing things she sees, hears, feels, smells, tastes in a moment. Avoiding stimulants such as caffeine and highly processed foods, and increasing protein regularity can help to ease anxiety on a biochemical level.
While temporary anxiety can benefit from some simple interventions, if her anxiety seems persistent, I would encourage her to find someone to work with for deeper support and more individualized care. Psychology Today or Good Therapy can be resources to find a therapist who specializes in social anxiety.
Best!