OK! Exclusive: Britney's Best Friend Moves Out

Only three weeks after , cousin, constant companion and best friend to beleaguered pop star , moved out of her own L.A. apartment to take up residence with the "Toxic" singer, OK! has learned she's telling friends she's had enough and is packing her stuff up.

"I can't take it anymore," the 21-year-old Alli has told friends regarding her high-pressure living situation, which includes chauferring Britney around and doing her shopping for her, all while being hounded by photographers.

But when OK! caught up with Alli to ask her why she's calling in the moving trucks, she had a different story to tell. "My move wasn't sudden," Brit's cousin claims exclusively to OK!, "I was just doing it slowly; I've had my own apartment all along."

What Alli's not saying is that this new apartment is in the very same Marina del Rey condo building where Brit's mom, , also happens to live. Coincidence? Not likely.

Meanwhile, the former Mrs. has holed up at the posh Peninsula Hotel in Beverly Hills. Perhaps now that she finally has a California driver's license, she no longer needs her best pal.