A: Hi Mom,
Your first step is to try to figure out what triggered your daughter's sudden desire to pull back from the social scene. A failure? Too hard of a class? Humiliation? That will help figure out next steps when you ease her back into "life." Generally a sudden switch in a child's "typical personality" that lasts (waning nothing to do with other kids) is due to a stressful experience.
Next, begin slowly with just one playdate - limit the time and hold her at your home. You want to help her warm up. Once she feels comfortable with one friend at your home you can suggest she venture out to the pal's house. You may need to stay for a while. The goal is to help boost her security.
It helps if you practice one new little social skill (saying hello or asking the pal what she'd like to play). It also helps if you allow warm up time - not pushing her too quickly. Also find a pal who she is most comfortable with - one who matches her interests and temperament.
Hang in there!