Police say she was on board a train between Canning Town Finchley Road on January 15 at around 11.30am, when a man sexually assaulted her.
An image has now been shared out of someone who police believe could provide more information into the investigation.
While a description hasn’t been officially provided, the image shows a Black man, with a beard, wearing a black coat and hood.
Anyone who recognises him is asked to contact British Transport Police by texting 61016 or by calling 0800 40 50 40, quoting reference 261 of 15 January.
Alternatively, you can contact Crimestoppers anonymously on 0800 555 111.
