You do need to know why, so I think that some kind of contact is necessary, not to beg, but to gather info and show concern:
1) does she consider group work to be wasted time and therefore a waste of tution expense?
2) does she have a behavior disorder (anxiety/panic) that is exacerbated by group interaction?
3) is there someone in her group that makes her uncomfortable?
4) did she receive a text message about a family member who died?
The list could go on, but until you have the right info, it is hard to make a judgement or to determine a 'next step'.
Erla's comment about getting some buy-in is spot on. If the group work is just a 5 minute exercise to brainstorm that is one thing. If the group work is a major project making up a significant portion of the grade, this could be a powder keg unless all the players understand how to stay away from the fuses that cause interpersonal explosions. If they have already had some success in doing some case study style brainstorming, it will not be as hard to get them to take it to the next level, and they will have some experience in dealing with each other.
