It was supposed to be a pretty cheerleader's dream Sweet 16 party.

But the $50,000 celebration turned sour when thugs attending a wedding at the same catering hall in the borough of Queens crashed the affair, molested teenage girls and walloped the guest of honor's cousin, a new lawsuit alleges.

Cheyenne Jeudy spent months preparing for her blowout bash, which included the teen performing three choreographed dance routines.

Her mom, Denise, an NYPD cop, spent two years preparing for the party, attended by relatives from as far away as Trinidad and Canada.

But according to a lawsuit filed by Denise Jeudy, the festivities turned ugly because Russo's on the Bay, a Howard Beach catering hall, had no security in place to prevent guests at another party from molesting young girls at the Sweet 16 and beating up her nephew outside.

The mayhem ruined what had been a perfect night for Cheyenne, a cheerleader at Lawrence High School on Long Island who aspires to join her mother in the NYPD.

"They [the party crashers] were drunk. They were feeling my friends up while they were dancing, pulling them down on the floor with liquor in their hands," Cheyenne said. "I was embarrassed."

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