To be frank, there is little you can do directly beyond providing her with attentive, supportive, understanding influence. Yes, it could be that she has a physical problem that causes the enuresis, bit I assume the pediatrician has ruled that out. Under strressful conditions, children often do display regressive behavior. Her daily enuresis and trichotillomania demand intensive intervention. It is likely that twice-monthly menatl health contact is not sufficient. Do you happen to know if she is prescribed any medication? Are you friendly with her father (or other guardian)? You would be helping her by suggesting that more intensive help be sought. An example of more intensive help would be a so-called partial hospital or day program. She would stay overnight at her home, but attend the day program instead of school for as long as needed to achieve stability.
I am friendly with her dad, but frankly I suspect the dad has a form of asperger's syndrome. He is very lacking in social skills and it takes him a long time to even talk to someone (when he used to call me about dance pickup times, sometimes he was too afraid to speak, even though on caller ID I could see it was him, I would then have to initiate conversation, and he would speak haltingly). Family friends have told me to leave messages on their home answering machine, so that the dad can "digest" the question or information. My latest voice mail to him has been about whether I could give his child feminine pads for her day wetting, but he has not called back about that yet. Anyway, I will carefully explore whether it would be an option for her to do more intensive therapy. Right now, like I said, they seem to go every other week.