Personal Hygiene for kids

This is a very difficult topic to write in a sensitive and pc way so before I begin I must stress that I mean no offence to anyone and am not in any way a racist or any other 'ist' of any kind.
I work with children and have recently begun transporting a young black girl to and from home, school and parental contact. She is in last year of primary school but is head and shoulders above the other kids and very mature, looking about 15. The problem is that she smells so very badly of BO that it is impossible to lessen the smell even with air con or windows open. Trapped in a car with her for an hour is extremely unpleasant but although I would be happy to have a discreet and sensitive word with her, I would probably lose my job. It should be done by parent, carer or social worker. This has never been a problem with the scores of other children of all races and cultures that we transport, only the odd whiff after a long, hot day, after all who hasn't at some time? I must add this is a problem for all the staff who drive and escort her but that none of us treat her any differently to any of the other children we work with. Any ideas or suggestions?