Kalie Machado says Britney Spears "needs mental help"

Kalie Machado , 23, a former Britney Spears assistant says she was Spears's drinking companion and shoulder to cry on.

Now living back in Northern California, Machado tells Us details of Britney Spears's breakup with Kevin Federline, and how Spears, 25, even desperately tried to win him back.

"She wanted so badly to have the father of her babies. When Britney thought about Kevin not wanting her, she would bawl," Machado tells Us. "She would look at Sean and Jayden and say, 'Where's your daddy? I need help. Where's your daddy?'"

And Sean Preston, 2, and Jayden James, 1, were with Spears when she and Federline had their final fight, something Machado says Spears felt she was tricked into. After following him to New York with their sons, "She stood up for herself, and it kind of backfired," Machado recalls. "That was what [Federline] wanted."

"She would ask, 'Why did he do this to me?'" Machado tells Us, adding: "It just made her crazy and depressed."

Machado adds "She needs mental help,"