"I don't think any agent would arbitrarily tell the girl or parents that the Secret Service will destroy or erase an investigation file either. The file maybe closed but it ain't goin nowhere."
I agree. Especially after a threat on the life of the President that was published on the internet so it could have provoked others. That file will not be erased.
Don't be surprised if this girls name comes up in the future, possibly on a different subject.