The woman was assaulted in the late hours of Friday evening at 11.15pm while she was walking with a friend in Wellington Place.
The group of youths left her with minor injuries to the chest and head.
A passer-by and the driver of a silver metallic 4x4 stopped to help the victim after the attack.
Police are urging for any witnesses to come forward as PC Daniel Moss, of Hastings response investigation team, said: "We would like to speak to the person from the silver 4x4 and the other person who helped the victim to see what they can tell us about what happened.
The attacker is described as a slim Afro-Caribbean woman standing at 5’8’’.