Friends found the 28-year-old lying on the ground in Victoria Street, having been knocked unconscious.
She needed hospital treatment for facial injuries after the attack which happened at about 12.45am on Saturday 5th July.
Two men were reported as running away from the scene. Both were white and one was said to have had dark hair and was wearing a blue T-shirt and jeans.
Neighbourhoods Manager Inspector Bob Evely said today: “We believe this is an isolated incident and would appeal for anyone who can help our inquiries into how this came about to get in touch either through the website or by calling 101.
“Alternatively ring the independent charity Crimestoppers on 0800 555 111. They never ask your name or trace your call.”
The reference number is 67836/14.