The victim is reported to have been approached from behind while she walked in Delce Road at around 11.30pm on Monday 19 April 2021, before being indecently touched over her clothing.
A computer generated image of a man officers would like to speak with was issued shortly after the offence took place.
As part of continuing enquires, officers arrested a 35-year-old man from Medway on suspicion of the sexual assault.
Due to the need to conduct further enquiries, he has been released on bail until Saturday 22 May.
Detectives remain keen to hear from anyone with information. Anyone who believes they can assist is asked to call Kent Police on 01634 792209 quoting reference 46/65332/21.
You can also contact the independent charity Crimestoppers anonymously by calling 0800 555111 or using the online form on their website.