The incident happened at around 11.30pm on Saturday on Evergreen Street in the city.
The woman suffered a broken jaw in the attack.
After reviewing CCTV, officers want to speak with a teenager - believed to be aged 13.
Ann Mooney, the southern correspondent with the Irish Sun, says he's now a person of interest:
"Watching that CCTV footage they saw a young man, a teenager- around 13 years old- who was following the woman around the street and whom they want to speak to. He's now considered a person of interest."
