The fairy-tale romance between Joel Madden and Nicole Richie has finally come crashing down, thanks to has-been Mischa Barton. Star Magazine says

For months they’d been fighting, but Nicole and Joel’s strained relationship hit a new low when she screamed at him, “we’re through,” and fled to her mother’s home, taking their daughter Harlow with her. Joel followed her to the Big Apple, and the quarrelsome couple made a disastrous appearance at [an] afterparty on Sept. 6. “There was obvious tension,” an eyewitness [says]. “I didn’t see her talk to Joel the entire night, and it seemed like he was avoiding her too. Nicole was just so angry!”

The next day, Joel headed back to L.A. [and] partied like he didn’t have a care in the world — with Nicole pal Mischa, [who had just] broken up with boyfriend Taylor Locke. [Mischa] was dancing seductively for Joel, says a source. “He kept checking out Mischa and smiling at her.”

Remember like five years ago when Mischa Barton was the new “it” girl? Now she’s swabbing the deck with Nicole Richie’s leftovers and hawking canvas tennis shoes. The only way Mischa could be any less relevant is if she were Joe Biden. Zing!

Nicole in West Hollywood last month:

Mischa at the Inspiration and Passion of Valentino Garavani in London yesterday:

BONUS NIP SLIP!!:

Lindsay Lohan was photographed earlier this week getting “friendly” with Nicole Richie’s boyfriend and father of her baby, Joel Madden. According to MSNBC

Spies caught the Good Charlotte frontman sitting up close and personal with [Lindsay] Monday night at a Cinco de Mayo celebration held at West Hollywood’s Crown Bar.

Eight out of ten women surveyed said they would rather see a grizzly bear covered in fire ants wielding a chainsaw next to their significant other than Lindsay Lohan. That goes double if she’s touching his knee with her legs open. She’s like some kind of a penis vampire, constantly on the prowl for semen and smegma to survive. I heard the only way to kill her is a shot of penicillin delivered by a priest directly into her puss under a full moon. True fucking story. Just to be safe, though, you might want to start carrying around a sterling silver condom and a rosary.

On the set of Ugly Betty May 3rd: