Britney Spears cousin and best friend Alli Sims got served early Sunday morning regarding custody of Britney’s kids as she was leaving a party.

At 2:30 a.m. on Sunday, Britney Spears‘s longtime pal, Alli Sims, was served with legal papers concerning the ongoing custody battle between Spears and her ex-husband, Kevin Federline, a source tells PEOPLE.

Sims was leaving a party at a private home in the Hollywood Hills when she was served by Aaron Cohen of IMS-Security.

“Alli was really shocked and covered her face,” an observer tells PEOPLE. “[She was] really distraught and said ‘Oh my God.’ ”

Spears, who was also at the party, did not witness the serving of the papers, according to the observer.

It appears Kevin Federline is trying to get full custody away from loco Brit.

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