The force deployed extra patrols near schools in Tonbridge following reports people in clown or Halloween masks were trying to scare pupils.
Tunbridge Wells Ch Insp Dave Pate said fancy dress was not unusual but he warned people not to cause alarm, distress or fear to others.
The 18-year-old woman was still helping police with their inquiries, he added.
Mr Pate said: "We are continuing to make inquiries to establish whether any offences have been committed.
"Whilst it's not unusual for people to be wearing fancy dress, including masks, I would warn everyone to celebrate responsibly and not do anything which may cause alarm, distress of fear to others."
He said anyone found to be committing an offence would be dealt with appropriately.
Police have also been investigating reports of people approaching children in Tunbridge Wells in vans but Mr Pate said those reports were not linked to incidents in Tonbridge.
He said local schools and officers investigating the van incidents had ruled out any possible crimes.
A woman who allegedly tried to frighten children by approaching them in a clown mask has been spoken to by Kent Police.