Officers from West Midlands Police were called to Castle Yard, just off Princess Street, in Wolverhampton at around 3.15pm on Friday after reports of a disturbance.
They found and arrested a 21-year-old woman from the city on suspicion of assault and harassment.
The woman remains in police custody while investigations continue.
A spokeswoman for West Midlands Police said: "We were called to Castle Yard in Wolverhampton shortly after 3.15pm today (Friday) following a report of a disturbance.
"A 21-year-old woman from Wolverhampton has been arrested on suspicion of assault and harassment. She remains in police custody at this time."