That provoked an angry reaction from the Palace midfielder, who grabbed Cain by the neck, before wrestling her to the floor. It was unclear whether Littlejohn tripped over a team-mate as the pair fell to the deck but her actions left referee Alice Parker no choice but to show her a red card.
The incident came in the 90th minute, with Palace already leading 3-0 at the time. They went on to win the game and progress to the knockouts.
Violent conduct is when a player uses or attempts to use excessive force or brutality against an opponent when not challenging for the ball, or against a team-mate, team official, match official, spectator or any other person, regardless of whether contact is made.
In addition, a player who, when not challenging for the ball, deliberately strikes an opponent or any other person on the head or face with the hand or arm, is guilty of violent conduct unless the force used was negligible.
Violent conduct offences usually result in a three-game ban but players can be given a longer suspension if their actions are deemed particularly severe.
Littlejohn, 35, has 93 caps for the Republic of Ireland and has played for clubs such as Arsenal, West Ham United and Aston Villa during her career.
