Tears as Britney's pal served with court papers to testify on the star's 'parenting skills'

Aspiring singer Sims was served on leaving a party at a private home in the Hollywood Hills. A shocked looking Sims was seen shortly after in tears as she sat in her car.

A source told People: "Alli was really shocked and covered her face".

"She was really distraught and said 'Oh my God.' "

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Are you being served: Britney's childhood friend Alli Sims was served with legal papers requiring her to testify on the star's parenting skills as she left a Hollywood party

Tears: A distraught Sims collapsed in tears after being served with the court papers

Federline's lawyer Mark Vincent Kaplan confirmed that Sims, Britney's longtime party pal, would give a statement "in connection with the Britney Spears - Kevin Federline issue".

He said the subpoena was delivered to Sims because she was "believed to have relevant information". Britney was reported to have been at the same party as Sims, but did not witness the serving of the papers.

She left the party hand-in-hand with a mystery man looking worse for wear, and at one point, tearful.

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Party on: The party never stops for Britney despite her looming custody battle with ex-husband Kevin Federline

Sims recently told People: "Britney is a wonderful mom and she is so hands-on. ... Britney loves those babies to death. And they adore her.

"I love her, she's beautiful inside and out. We're still great friends."

Ex-husband Federline has filed for primary physical custody of their two sons.

Federline is reported to be concerned about his former wife's increasingly erratic behaviour and believes she is exposing their children to "unnecessary risk," according to sources.

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Dancing queen: Britney continues her partying despite her looming custody battle

In recent weeks reports have surfaced of her causing £10,000 worth of damage at a photoshoot, crashing into a parked car and cavorting topless with a man she barely knew during an alcohol-fuelled night out.

"All of these things that come out (about Britney), if true, are things that would concern me," said Federline's lawyer Mark Vincent Kaplan.

"(Kevin's) desire is that these kids have a chance to grow up free, in as normal an environment as possible," he added.

The couple's divorce was finalised last month. Since February, Spears, 25, and Federline, 29, have shared joint custody of their sons, 22-month-old Sean Preston and 10-month-old Jayden James.