No one would watch her twenty-four-seven to see that she is not having sex. The way she would get caught most likely is if her parents tell on her. It could also be one of her friends or she could admit to it. Typically the way that would come about is that she would sneak out and get caught at some boy's house late at night or something like that. She'll have a hearing on a petition to revoke probation or just a review hearing on her juvenile case and any of her violations will be brought to light. If this is a juvenile case like I suspect it is, there are probably several pages worth of conditions of probation and violating any of the long list of conditions could get her probation revoked. Even if it's not a case in juvenile court no doubt there are several other conditions besides those mentioned in this article.
Both of you finnaly get my point. where are the parents? and it should be up to them to insure that their daughter doesn't have sex not our nanny state court system