Jessica Simpson "Betrayed" By Vanessa Minnillo  6/22/06

Jessica Simpson is furious with former friend Vanessa Minnillo and insists the TV presenter has betrayed her by dating her estranged husband Nick Lachey.

Minnillo and Simpson became fast friends after meeting at an MTV event in 2003 and frequently enjoyed "girls' nights out" together.

And now Minnillo's father, Vincent Minnillo, confirms, "Vanessa is friends with Jessica. In fact, (Vanessa, Jessica and Nick) have gone to clubs together and had fun."

The trouble between the former pals reportedly began when 32-year-old Lachey asked Minnillo to star in his music video What's Left of Me, which documents the end of his marriage to Simpson.

A source says, "Jess was bothered by that, but she was willing to let it slide because she knows how badly Vanessa has wanted to get into acting."

To make matters worse, Simpson confided in her friend when her marriage was breaking down and Minnillo encouraged her to leave Lachey if she wasn't happy.

After seeing steamy photos of the new couple kissing in Mexico, Simpson was crushed even further.

The source adds, "It's painful and hurtful, but it just reinforces her decision to leave Nick."