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A screaming match with her ex-husband, Kevin Federline, left Britney Spears reeling - and, after a public breakdown, running for rehab, sources said Tuesday.

As a fitting finale to a series of strange events that led Spears to shave off all her hair last weekend, Spears entered a prominent Malibu, Calif., treatment center Monday night.

"Britney Spears has voluntarily checked herself into an undisclosed rehab facility today," her manager, Larry Rudolph, said in a statement. "We ask that the media respect her privacy as well as those of her family and friends at this time."

Photos confirm Spears has checked into the posh seaside celebrity haven Promises. She was spotted strolling the lush grounds Tuesday in a hot-pink tank top and pants that appeared to still have the sizing sticker attached.

Spears had removed her ill-fitting blond wig and was photographed scowling and smoking a cigarette.

Rudolph said Tuesday that the decision for treatment was Spears'. In a call to E! News' Ryan Seacrest, Rudolph said he had just spoken to Spears and that she told him all she wants is time to rest, to get better and focus on her recovery.

According to OK! magazine, it was a blowout with Federline that sent Spears reeling over the edge.

"They had a huge argument," a source told the magazine. "Kevin threatened Britney that he was going to have people test her hair to find out exactly what she's been up to. She was so scared. That was what made her have her head shaved."

Testing her hair could determine whether she had been abusing illegal drugs, which could be used against her in the looming battle for custody of their two young children.

Spears' friends say the detoxing diva was bowing to pressure from Federline, friends, family and Rudolph, who pleaded with her to return to rehab.

A typical stay at the resort-like center, tucked in the Santa Monica mountains, is around 45 days. Patients often share a room, attend group and individualized therapy sessions and do chores. Estimated costs for a stint at the plush facility is between $40,000 and $60,000.

On Monday, Richard Rogg, founder and CEO of Promises, said Spears' original short-lived visit to the Crossroads rehab facility in Antigua last weekend was an act of desperation.

"It usually happens when someone is coerced into being there, or they're so drunk and loaded that they come into treatment - wake up, and they're gone," said Rogg.

Promises boasts a who's-who of Hollywood alumni, including Ben Affleck, Robert Downey Jr., Matthew Perry, Charlie Sheen and Diana Ross.

As Spears strolled the center's grounds, a fleet of paparazzi was flying overhead in helicopters with the doors removed, hovering over the facility to snap lucrative shots of the recovery-seeking songstress.