The symptoms suggest that the girl has laryngitis, a throat infection. In most cases of throat infection the cause is viral, the condition is self-limiting and can be treated symptomatically with over-the-counter medication. However, the cause may be bacterial, with antibiotic treatment required. In this case you could recommend an anti-inflammatory – ibuprofen tablets or liquid, or flurbiprofen lozenges – with advice that if there is no improvement within two days the GP should be contacted and informed that OTC medication has been tried but has been ineffective.