The best thing you could do for a friend in this situation is to help her get professional help. It is very important for people who suffer from anxiety or some other mental disorder to have a good circle of friends that provide support. However, its much more important for them to get the professional help they need. Depending on your friend's symptoms, she might require therapy, or medicine. However, only a qualified professional could make this assessment. The best thing you can do is helping her find this information, and trying to provide company and support along the way.