@Foolseverywhere I don't get your point?
The SW went to the wedding - an islamic ceremony could have been a very short and private 'ceremony' in a situation like this, they're often held in the couples home with minimal people attending. It's entirely possible that a SW could have gone and done so without running it past a manager or telling them what he was doing, or minimising his involvement. It isn't necessarily something that the manager or department would have known about let alone supported.
Sadly Muslim women and girls are not protected under UK law, if there had been a legal aspect to the wedding it couldnt have gone ahead (obviously being illegal due to her age, but if under 18 it would have needed the explicit consent of the director of children's services and that would not have been given, as she was on a care order theres a chance the court would have needed to be notified also)