The woman, who is in her 20s, suffered bruising to her eye in the attack, while the suspect fled the scene.
Officers have released an image of a man who is wanted in connection with the attack.
A BTP spokesperson said they believe he may have information that could help the investigation.
The attack was revealed less than 48 hours after a man was assaulted with a hammer and pushed onto the tracks at All Saints DLR station in east London.
The victim, who is in his 30s, was hit over the head with the hammer and suffered a fractured skull before being pushed onto the tracks.
His injuries were not described as life-threatening and he managed to get off the tracks to safety.
The hammer attack took place at 10.43pm on Monday 29 July.
Detective Superintendent Nick Sedgemore, from BTP, said: "Clearly this is a very concerning attack. Enquiries have been underway since it occurred to locate the suspect and understand his motive.”
Police are asking anyone who can identify the man wanted in connection with the New Cross Gate attack to contact BTP by texting 61016, or by calling 0800 40 50 40, and quoting reference 54 of 07/07/19.
Anyone with information on the hammer attack has been asked to contact BTP on those same numbers, quoting reference 670 of 29/07/19 instead.