Jasmine and Casey were besties until the latter allegedly broke into the former's apartment. There, Jasmine says, Casey masturbated in her bed, then left the used vibrator bewteen the sheets and absconded with a grand theft's worth of jewelry, clothes, and panties. Now Jasmine's speaking out about Casey's insanity—but who, you ask, is Jasmine?

• She's Trainwreck Royalty Papa was a playboy shoe magnate, Mama was a 1970s Bond girl. According to their mother, Jasmine and her sisters were named after three of their father's mistresses, "a tribute to those who didn't make it." Jasmine's parents divorced when Mom realized Dad had gambled away the family fortune, and Mom went on to fake a pregnancy and say this other lady's fiance was the daddy, which led to a nasty little lawsuit in 1995.
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• She's an Early Bloomer Jasmine started modeling at 14. By 17 she had, according to the London Evening Standard, stolen thousands of pounds from her mother to pay off menacing drug dealers, and even checked into five-star London hotels for three-day sex and drugs orgies, with bowls filled with high-grade cocaine," and once did a stint at the Priory alongside Kate Moss.
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• She's a Reality TV Villain Who Catfights Above Her Weight Class Jasmine was the "rich bitch" of Britain's Make Me a Supermodel's first season, causing supermodel host Rachel Hunter to muse aloud about wishing Lennard would get stung by a bee and die. Jasmine later got a job hosting an Make Me a Supermodel spin-off, but was fired for calling Hunter "Rachel Munter" (apparently it's a really bad word in England?) and "a fat bitch past her sell-by date who cost me winning the show" and "fat, spotty, and finished" and "I suggest she throws out the truckload of make-up she uses and hire a personal trainer."
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• She Dates Men and Women, Young and Old Paramours allegedly include Simon Cowell (while he was dating Terri Seymour), Hugh Grant, and Courtenay Semel, Casey Johnson's on-again off-again "lesbian Don Juan" heiress girlfriend, who blew the whistle on Casey's alleged crime when she recognized Jasmine's panties on Casey and sent Lennard a text message:
  

  There's a problem, Jaz, Casey Johnson just got into bed with me and she is wearing your underwear. You need to call police. There are documents here, your shoes and your clothing—you need to call the police.

  Jasmine's not gay, it's just that she is just very beautiful, and so are her friends, so sometimes it's hard to resist:

  I meet a lot of beautiful girls working in the modelling industry and I prefer to look at them rather than men, sometimes. I'm not a lesbian. ... But being with a woman is a totally different sexual experience. They're soft, with curves, boobs and sensual lips.

• She Was Friends with Casey Johnson Until Casey, Like, Fell in Love with Her Isn't it so annoying when you take a drug-addled, emotionally damaged heiress under your wing, but she totally bites the hand that's feeding her, because she is such a hungry bitch and does not have as much self control with food as I do, because, gawd, I'm awesome:
  

  Since the day I met Casey, I have only been a good force in her life. ... I tried to get her off drugs and alcohol. ... I've given her money. I am the only person who helped this girl, and I believe she was obsessed with me, and thinks in her mind we had some kind of affair.

  This time she really messed with the wrong lady. I am going to teach her a lesson

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• She Enjoys Lollipops Jasmine was in Guy Richie-directed Revolver, where she shows her panties and satiates an oral fixation in a scene interspliced with a gory shoot-out.
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And now comes photographic evidence of their reconciliation — all smiles, hair extensions and fire extinguishers just off-camera as the fraught lovers recently filed their way through some of this year's finest cinematic offerings. We take them for the Vicious Kind type, or maybe It Might Get Loud?Adventureland on a good day? Either way, they seem to have the festival under control; between confirming their presence and authority on the scene, our work here appears done.

• Courtenay Semel and Casey Johnson, back together at Sundance! [NachoFoto]

We can't make it up, and we doubt Page Six would either: The revelation followed word that Casey Johnson has recently adopted a butchy new post-inferno coiffure since last visiting Semel — a meeting which itself followed another Johnson fight with her current girlfriend. A surge of "dumb fuck"-calling no doubt culminated in a climactic Google-Off during which Semel's name mustered 15% of Johnson's 1.4 million hits, thus provoking Semel to flamethrowing fury:

[A source said] "Casey went to Courtenay's house, and Courtenay proceeded to beat the crap out of her, and then she lit her hair on fire. Casey had to be hospitalized." Casey's mother, Sale Johnson, reportedly flew to LA and consulted with lawyer Robert Shapiro. No one returned calls except Courtenay, whose father Terry Semel ran Yahoo for years. "There was a fight," Courtenay said. "But this is a major exaggeration. We are speaking."

We're optimistic this can work itself out, but Johnson may want to consider bodyguard accompaniment until then. There's a good security guard in Vegas looking for work, and as far as we know, he comes with a Semel restraining order already issued. Give him a ring.

• EX SETS CASEY'S HAIR ON FIRE [NYP]

But her recent detention in Vegas after a drunken, assaultive visit to Caesar's Palace is what really compelled our consideration here: Who is this Hebrew hellcat, anyway? After the jump, learn everything worth knowing about Semel's climb to sort-of fame.

I. KNOW YOUR SEMELS

Courtenay, 28, is one of three daughters born to billionaire ex-Warner Bros/Yahoo! chief Terry Semel and Jane Bovingdon Semel, a former secretary to Susan George. She attended the Loomis Chaffee School in Windsor, Conn., before abandoning education for... we don't know. This is a historical gap we have yet to fill in; suggestions are welcome.

Regardless, she's clearly been doing some philosophizing over the decades, culminating in the powerful declaration of principles held forth below:

II. KNOW HER CANON

Courtenay got her start in 1991, portraying the crucial role of "Bratty Kid" in the Bruce Willis flop Hudson Hawk. Her 2000 follow-up — the never-released indie thriller Sweetie Pie — is best known for a cast also including Paris Hilton, Whitestarr vocalist Cisco Adler and the offspring of Dustin Hoffman and Kelsey Grammer.

Her "break" (and all of ours, really, if we're being honest) came when she was cast alongside childhood friend Kourtney Kardashian, George Foreman III, Fabian Basabe, Brittny Gastineau, Shanna Ferrigno and other nepotism all-stars on the 2005 E! series Filthy Rich: Cattle Drive. The show featured Courtenay and Co. skipping the boilerplate South Beach coke getaways for a bit of reality-TV ranch-handery. Sadly, due in part to reasons listed below, it was not renewed for a second season.

III. KNOW HER ACCOLADES

Courtenay's otherworldly bitchy contribution to FR:CD was roundly commended by critics who cited her distinctive look ("like an overfed mutant chipmunk") and her performance as a "brattier, PMS’ing version of Haley Joel Osmond [sic]" — outmaneuvering even Basabe as the worst human being the show had to offer. Word is her father was happy with the performance in Hudson Hawk as well, but as of press time he has not responded to Defamer's requests for official comment.

IV. KNOW HER STYLE

Spoiled lipstick-lesbian chic, at once aggressively designed and thoroughly disposable — all spangles, trash, heels and hair.

V. KNOW HER LOVE LIFE

This is where it gets complicated. Courtenay has been very publicly attached to no fewer than three young women of varying celebrity since 2007, starting somewhat retroactively last winter with Lindsay Lohan. "Everyone thinks Samantha [Ronson] is Lindsay’s first lesbian love, but we were very passionate until her fear of being found out drove us apart," she was quoted as saying. "At the time she was terrified her career would be over if she revealed her sexual tendencies. But then Samantha came on to the scene and I was dropped.” That triangle was fleshed out a little more this week by our cousins at Gawker, who noted that Courtenay and Ronson both visited LiLo separately during her rehab residency.

Next came Johnson and Johnson heiress Casey Johnson, who made the gossip rounds last month after a canoodling binge with Courtney. Enter Tila Tequila, who showed up maybe a week ago? A couple weeks ago? Anyway, now they've found true love, as evidenced by the scorching red-carpet chemistry below:

Surely she must also have been some poor bastard's beard somewhere along the way; as always, your tips are welcome!

VI. KNOW HER EMPIRE

You mean besides her father's 10-figure net worth, divided four ways sometime in the next 15 to 20 years? Not so much. We guess she can always lobby for a Filthy Rich: Cattle Drive — The Complete Series DVD Box Set, even though Basabe probably has a 75/25 split written into his deal. He thinks of everything.

VII. KNOW YOUR FUN FACTS

· Has been a Kardashian family BFF since the age of 2.

· Intimate public displays of affection with Tila Tequila range from kissing to spoon-feeding ice cream in VIP areas.

· Reportedly drove off from this year's VH1 Rock Honors with Casey Johnson in a $160,000 Mercedes that wasn't theirs. They returned it a few minutes later.

Did we miss something? Chime in below — we're nothing without you.

[Photo Credits: Getty Images]