To work with anyone in a Gestalt way is to look for what is figurative for them at that time, and respond accordingly. Adolescence is, as I am sure you are aware, a most confusing, self-conscious and frightening time. Adolescents are struggling with a state inbetween that of child and adult. They swing from one to the other. Their changing bodies cause great anxiety and self-consciousness, and they are often so testing that compassion is very hard to maintain, especially for parents.
Good empathy is particularly important.
A lot of this is common sense. I would be interested to know more about your work, and what you do do with your client, how Gestalt fits in. I look forward to more from you on this noticeboard.