Brit wrote and delivered a poem to Lynne called, “Dear Momma�? in which, says a source, “she told Lynne that she didn’t have a mom anymore and she couldn’t imagine a mother doing what she did to her child.�?

The showdown officially began on June 28 when Brit arrived on the Valencia, California, on the set of Jamie Lynn’s TV show, Zoey 101. She quickly found the startled Lynne, and coldly gave her a package filled with legal documents and a CD. “Britney said, ‘Here Momma, I just wanted to see your face,’�? says a source. “Then she got into her car and drove off. Lynne went into the trailer and broke down in tears.�?

The CD in the package was of recordings of phone conversations Lynne had with Kevin and others regarding Brit’s well-being – which she obtained with the help of a private investigator, says a source!

A source claims in one conversation, Lynne made arrangements to meet up with Kevin and the kids, and is then heard saying, “I have to be careful that Britney doesn’t find out!�? In another call, referring to the couple’s ongoing custody and financial battles, “Kevin told Lynne that he had everything under control,�? adds the source. “He was just going to let Britney hang herself in court.�?

Britney also presented Lynne with a copy of a legal motion to keep her away from grandson, Sean Preston, and Jayden James. The papers contain allegations that at Lynne abuses prescription drugs and abuses her grandsons when she is with them!�? says the source, noting that the charge of “child abuse�? in the motion refers specifically to Lynne speaking negatively about Britney in front of the tykes.

As a final blow, Brit cut Lynne out of her will – covering an estimated $100 million fortune and now “is leaving all of her property and personal belongings to Jamie Lynn until her boys are of age,�? says a source. “Britney is using her money to win over her sister, but Jamie loves her mom and her sister, and doesn’t know what to do!�?

Britney, the source adds, “thinks that everyone sits at Kevin’s house and has one big laugh at her expense. She wants to put an end to this by humiliating her mother publicly. Lynne loves both Brit and Kevin, and is afraid if she doesn’t agree to Britney’s demands, she may never have a relationship with her grandsons or her daughter.�?