"Basketball Wives" star Jennifer Williams is finally fighting back after being slapped in the face by her reality show nemesis Nia Crooks ... with a big, fat, stinging lawsuit.
TMZ broke the story ... Williams filed a police report after the January 21 incident, in which she claims Crooks delivered an "open hand" slap to the left side of her face during a group outing to a race track in Florida.
The incident was caught on tape by the "Basketball Wives" crew and aired last week. During the melee, Crooks threatened Williams right before the attack ... saying, "Do I need to slap you in the face to wake you up?"
Williams replied, "I wish you would." She got her wish.
Williams has now followed up with a civil suit in NY ... going after Nia's ass for assault and battery. In the docs, obtained by TMZ, Jennifer claims she suffered serious injuries in the attack ... as well as "mental shock, mental anguish and psychological trauma”
Williams is demanding Nia fork over a massive check for all of her medical expenses and other damages.
Calls to Crooks have not been returned.