From several sources
Apparently of the 12 boys 3 admitted to having consensual sex with the girl and some videoing took place and was shared online, there was no evidence against the other 9. The boys claim to have been beaten by the police, so the investigation seems to have bee robust.
So it was the usual story of her word against their’s, if it had happened in the UK it would it have gone to court. Maybe, but it would be very difficult to get a conviction in those circumstances.
As for her retracting the allegation, she should have had a lawyer present, who may have advised her not to, then there would have been a rape trial, very doubtful outcome.