Hannah Phillips, of Havant, Hampshire, was due to appear at Portsmouth Magistrates’ Court in connection with the incident which happened on the night of 5 August.
But the case was withdrawn by the Crown Prosecution Service after the court was told she had been given a conditional caution.
The charge against her stated that she had “intentionally touched a man aged 16 or over and that touching was sexual when he did not consent and you did not reasonably believe that he was consenting”.
Two other women, both aged 19, were also charged in connection with the incident at the Portsmouth nightclub and their case is to be dealt with separately at the crown court.
Prosecutors say the incident was sparked after a woman challenged a group after a man was slapped on the bottom.
Scarlett Bareham and Fiona Hoyle, both 19, are accused of affray over the incident with Bareham, from Havant, also facing a charge of sexual assault.
Hoyle, from Southsea, is also charged with assault occasioning actual bodily harm.
Both defendants entered no pleas to the charges at an earlier hearing and the case was sent to Portsmouth Crown Court for a plea and trial preparation hearing on 20 September.
Additional reporting by Press Association