Naomi Watts admits to having been cheated on. What she wouldn't discuss is who betrayed her. The gorgeous Aussie expatriate did split from the 10-years-younger, fellow actor and Aussie, Heath Ledger, in May, ending their two-year, on-and-off relationship. Heath is reportedly dating a covey of cuties and this month will travel to Venice to begin shooting director Lasse Hallstrom's romantic comedy for Touchstone, aptly named Casanova, opposite Sienna Miller, Jude Law's girlfriend.

While Naomi may be in a bit of a romantic dry spell at the moment, her career "couldn't be any more satisfying," the blonde beauty told us at the premiere of her new picture, We Don't Live Here Anymore. The film chronicles the sexual misadventures of two couples, best friends, who enter into provocative affairs with one another's spouses. Naomi and Peter Krause play one of the couples. Laura Dern and Mark Ruffalo play the other. Dern and Ruffalo were also at the after-party screening, as were screenwriter Larry Gross, director John Curran and producer Jonas Goodman. The film marks the return of Dern, who's been off-screen for three years. The consensus is that this comeback will most likely get her an Oscar nomination.

Naomi signed on for that role after wrapping up another demanding part in The Assassination of Richard Nixon, in which she appeared opposite her 21 Grams co-star, Sean Penn. "The character of Edith (in We Don't Live Here Anymore), was just too much of a challenge to pass up," said Naomi. It also provided her with the opportunity to work with her good pal, Mark Ruffalo. The two have known each other for years, when Mark was a bartender and Naomi was a regular at the hip eatery, The Olive. "When Naomi's career took off, she began talking me up in the industry," said Ruffalo. "Not too many fellow actors would do that." He also said that he considers Naomi one of his and his wife Sunshine's best friends.

We reported a month ago that Monaco's Princess Caroline was presenting her daughter, 18-year-old Charlotte Casiraghi, to society at the Villa la Vigire in Monte Carlo. Quoted from a guest at the coming-out party who would only speak on the promise of anonymity: "She was absolutely stunning!" Princess Charlotte was feted with a number of birthday parties, all of which were off-limits to the press. In fact, we were told, the security was so tight that even close friends were asked to check their cameras at the door. And of the only two members of the fashion press who were invited, both were asked to sign confidentiality agreements, causing one of them to grouse, "It's a real pity that no one gets to see a photo of the lovely Charlotte in her beautiful, flesh-toned Chanel gown." We were told that this is what she wore to her Saturday night ball. We were also told that Princess Caroline insisted that Karl Lagerfeld destroy his sketches of the dress.

One source told us they wanted everything "to be totally private." Festivities included a beach party and a Sunday brunch with more than 100 police officers and bodyguards on hand to keep the paparazzi at bay. At the beach party, Charlotte and some of her pals wore new Lagerfeld-designed t-shirts, made especially for Disneyland Paris to mark the 70th birthday anniversary of Donald Duck. One design depicts Donald a la Lagerfeld: high-collar, ponytail, and dark sunglasses (what, no fan?). The t-shirts were produced in a limited edition of 3,000 pieces and Charlotte and her friends were among the last of the fashion flock to get theirs. But to those who cannot live another day without one of them, another run is already being planned by Disney.

Our spy also told us that one of Charlotte's invitees gave her a Michael Kors-designed mink beach towel, emblazoned with "Capri." Charlotte was heard complaining, good naturedly, "Why couldn't it say Monte Carlo?" Well, at a cost of $14,000, we can only hope Charlotte's comment, good-natured though it may have been, didn't reach her guests' ears.

Before Michelle Pfeiffer begins working on her next project, Chasing Montana, written by hubby David E. Kelley, the happily married couple is getting their new San Francisco Bay home all spruced up, thanks to yeoman help from social powerhouse Ann Getty. Mrs. Gordon Getty's new business, The Ann Getty House Collection, has wonderful furniture, many pieces of which are custom made-utilizing drapery and upholstery fabrics and carpets-much of it replicating the Gettys' own original pieces from their San Francisco home. The collection can be found locally at the Pacific Design Center through Randolph and Hein.

Ann and Michelle have become fast friends and the Kelleys, through Ann's good graces, have become popular with San Francisco's society swells. All the city's top hostesses-Denise Hale, Danielle Steele, and of course Ann Getty-want Michelle and David at their dinner tables to add a little Hollywood glamour to the Bay Area's benefit circuit. "We haven't seen stars since Sharon Stone left town," says one of the city's young socialites.

All this is keeping Michelle and David very busy, of course. Michelle never wears anything but Giorgio Armani. In fact, in 1990, the famous designer created the simple navy silk jacket with draped skirt that the beautiful star wore to the Oscar ceremony in 1990, in which she was up for Best Actress in The Fabulous Baker Boys. That began their relationship and since then, they have become quite a fashion match-not unlike Audrey Hepburn and Hubert Givenchy, Liza and Halston, and Streisand and Donna Karan. We understand Mr. Armani sent Michelle a slew of gorgeous evening gowns for her to choose from as she attends the many glamorous black-tie parties she and David have been invited to this fall.

Tabloids report that Reese Witherspoon and Ryan Phillippe's five-year marriage is on life support prompted Witherspoon to call the stories "a bunch of someone's hot air spreading these rumors." The hotter-than-hot box-office queen's new film, Vanity Fair, opens this month. Directed by Mira Nair, the movie is based on William Makepeace Thackeray's classic novel of the ambitious, social-climbing schemer, Becky Sharp, who lets nothing block her entry into London's Regency circles. This is a role that Reese must've had to research thoroughly, as this Louisiana-born blonde is a true blueblood, with one of her ancestors having signed the Declaration of Independence. Previously filmed by RKO in 1935 as Becky Sharp, the movie earned Miriam Hopkins an Academy Award nomination for Best Actress. Reese essays the same role, and we're told that her performance is definitely Oscar worthy.

The Phillippes routinely eschew Hollywood parties, preferring instead to stay home with their two kids, and occasionally host the small dinner party where the table is set with monogrammed napkins that Reese embroidered herself. Reese has made her family her first priority, rejecting projects that are in conflict with her home life, and alternating film commitments with her husband so that one of them can always be at home with the children.

Ryan temporarily put his career on the back burner while Reese was involved with Vanity Fair as well as her current film, Walk the Line, a movie about the love affair and marriage of Johnny Cash and June Carter. During her absences, Ryan chauffeurs daughter Ava all over Los Angeles to pre-school, ballet classes, birthday parties, and play dates. The tabloids' baiting of Ryan, disparaging him as "Mr. Mom," should instead applaud this wonderful young dad as "Father of the Year." We wish we had had such a dad when we were growing up. We have learned that Ryan's excellent stint as a stay-at-home dad will be rewarded by Reese with a little trip to Venice, Italy, a kind of second honeymoon for this loveable and loving pair. The couple will also make an appearance at the 61st Venice International Film Festival, where Vanity Fair has been entered in the competition. Director Mira Nair, and Oscar-winning screenwriter Julian Fellowes, who adapted the novel for the screen, will also be on-hand in Venice.

Mariel Hemingway, the granddaughter of the late Nobel Prize author Ernest Hemingway and sister of the late supermodel and actress Margaux, is set to portray California's first lady, Maria Shriver, in the A&E biopic, See Arnold Run, which will detail Arnold Schwarzenegger's rise to prominence as the Golden State's governor. Roland Kickinger and Jurgen Prochnow will play Arnold at different ages.

It was back in 1978 when we first met the tall, teenaged Mariel in New York, where she'd come to appear in sister Margaux's film, Lipstick. In fact, we sat with Mariel and Brooke Shields at the "kids table" at the Studio 54 Oscar party, co-hosted by Andy Warhol and Truman Capote. Brooke had just wrapped Louis Malle's Pretty Baby and Mariel was about to start filming Woody Allen's Manhattan-a role that would earn her an Oscar nomination for Best Supporting Actress.

We hadn't seen Mariel in years when we ran into her and her producer husband Stephen Crisman at the Coffee Bean & Tea Leaf on the Sunset Strip. Mariel told us that Maria Shriver sent her a very nice note telling her to "have a good time [with the film]." We later heard from someone else that the note also said that Maria didn't believe in "this sort of thing" (i.e., making an unauthorized biographical film).

Paris Hilton showed up at the Teen Choice Awards in a flowing pink and peach chiffon evening gown, designed by Jennifer Nicholson-one of her seven costume changes during the ceremonies. But our friend Jennifer's design was far and away the most stunning of the bunch. Jennifer recently hired Amanda de Cadenet to shoot Sophie Dahl in her company's first advertising campaign. She has said that fashion, unlike acting, allows her to stand on her own without being in the shadow of her triple-Oscar winning dad, Jack. Jennifer did make a few film appearances, and was constantly being compared to Jack. Now, Jennifer is doing her own thing by designing fabulous fashions.