Born into the Johnson & Johnson clan's billions, Casey Johnson was among the first celebutantes to decamp to Hollywood in search of 21C fame. She died alone in a crumbling Mulholland Drive mansion, her body undiscovered for days.

She was 30 years old.

In her relatively short life, Casey embodied a number of romantic, moneyed archetypes. Raised amid fabulous wealth on Fifth Avenue, Casey was a precocious Eloise, receiving her first Chanel purse at the age of ten. She was Gossip Girl's Serena van der Woodsen, graduating from a tony Manhattan private school and enrolling at Brown — only to drop out freshman year to intern for queen bee publicist Lizzie Grubman. She was Paris Hilton's foil before Nicole Richie was. (Turning down Nicole's role in The Simple Life was "the worst mistake in my life.") In her final year, alleged mental and chemical troubles led to her family cutting off her finances, turning Casey into a lonely Grey Gardens dame:

Her house on Mulholland Drive is a mess. The electricity is off, there are rats, the pool is green. She was supposed to be evicted and her Porsche is being repossessed.

And now she is an exemplar of the painful, public collapses that keep happening at the juncture of privilege and fame.

In her final months, Casey's family and loved ones distanced themselves from her. Mother Sale Johnson (divorced from Casey's father Woody Johnson, owner of the New York Jets and great-grandson of a Johnson & Johnson founder) had apparently cut Casey off in an attempt to force her daughter into rehab. Sale took over custody of Casey's adopted daughter Ava, after friends said Casey would abandon the girl for days at a time to party. Girlfriend Courtenay Semel swore Casey off after a mutual friend accused Casey of breaking into her home and discarding a used vibrator in her bed.

Into this vacuum, hardknock stripper-turned-reality star Tila Tequila alighted suddenly—but with considerable fanfare—last month. In lingerie and full makeup, Johnson and Tequila announced their engagement on Tila's livestream web channel, under the headline "MEET MY NEW FIANCE CASEY JOHNSON HEIRESS OF JOHNSON & JOHNSON EMPIRE!" Diamond necklace shimmering and breasts heaving, a silent, smiling Casey looks on while Tila shouts "bam!" and waves a "17-carat diamond ring" before the camera.

The effect is tawdry, even by non-scion standards. In one video, Casey chases her pet dog down the street in her underpants. The hashtag #TilaAddiction appeared frequently in the heiress' Twitter stream—including during supposedly live-tweeted pleasure sessions. Casey's final December 29th tweets—and thus the final record of her life—coincide with the last time Tila claims she saw Casey, before the pair fought and fell out of touch, perhaps because Casey turned off her phone.

Casey's earliest scandal came to define the generational divide between the Jackie Onassis-cast socialites of yore and the nipple-slipping Paris Hiltons of today: At the age of 26, Casey accused her aunt Libet Johnson, 56, of seducing and stealing her boyfriend—all on the New York Post's Page Six, where Casey ridiculed her middle-aged aunt's love life, sex life, and emotional state. In a Vanity Fair profile, Suzanna Andrews writes,

[P]eople felt that they were watching more than just a delicious feud inside one of America's richest families; it was a changing of the guard, in which a generation steeped in decorum and jealously guarded privacy was giving way to a tougher breed, one given to using obnoxious exhibitionism, louche MySpace offerings, and bad press as social weapons.

The five-times-married Libet had, of course, had a dramatic personal life before Casey intervened. But Libet's generation's sense of decorum — coupled with Libet's obsessively controlled zone of personal privacy — had never been violated quite so spectacularly. The dignified Libet had finally met her match, and it was her photogenic, snarling cherub of a niece, stooping to conquer. The mercurial Casey Johnson — known to at least one member of Libet's generation as "the dreadful Casey Johnson" — became one of the enfant terribles of a new Hollywood class of cat-fighting rich girls. Casey reportedly instigated the violent spat between Bijou Phillips and Playboy Playmate Nicole Lenz that ended in several lawsuits, as well as a Bungalow 8 brawl in which Nicole Richie accidentally sliced open her boyfriend's face with broken glass. She posed on the red carpet making out with women, tweeted about her sex life, blew kisses to the paparazzi. She was reportedly obsessed with fame, particularly in starring in a reality TV show, even as she claimed to have left New York to get away from Page Six and Manhattan's society-watching vultures. Maybe she was lying about it, maybe she changed her mind—or maybe the brighter lights and higher drama of Hollywood just suited her better.

Casey wasn't the only Johnson to break from the family's scrupulously well-mannered styling; while Casey was clashing with Libet and her peers, her close-in-age uncle (i.e., cousin-like) Jamie Johnson was directing Born Rich, an HBO documentary that won two Emmy's for its portrayal of children of privilege, and the pathos of having too much.