If you haven't already read the discussions of Avoidant Personality Disorder in Clinical Applications of Cognitive Therapy (second edition) and in Cognitive Therapy of Personality Disorders (second edition), I'd recommend both of them.

It can be quite useful to help the client recognize the drawbacks to avoiding unpleasant emotions (especially anxiety and embarassment) and to help them recognize the value of persistently facing situations and emotions that they have been avoiding.