Principles of medical law and ethics practice

A 15-year-old girl is brought to a general practice by her mother, who is worried about three months of falling grades, weight loss and irritability. After the mother has described her concerns you ask her to wait at reception. The girl folds her arms, says she did not want to come, and adds that her mother reads her phone messages. You plan a full psychosocial assessment and every option below will be covered during today's consultation. Which one of the following should you do first, now that you are alone with her?