Rah Ali tried to exact vengeance against her archenemy and reality TV foe, Sky, in a sneak attack at Diddy's New Year's Eve "Black Excellence" party ... but Sky quickly caught on. TMZ has obtained video of a fight between VH1's 'Love & Hip Hop' star and "Black Ink Crew" bruiser Sunday night at Diddy's crib in

Miami, as the 2 met up on the black carpet. You see Rah say "hi" to Sky, and then act like she's going in for a hug ... before grabbing the back of Sky's head in an aggressive manner. Sky immediately starts hitting back, and the pair falls into Diddy's Ciroc backdrop before being broken up.