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When Kate Gosselin finally filed for divorce from husband Jon on June 22—after months of tense fighting, doubts about each other's faithfulness and relentless paparazzi attention—the reality TV star and mother of eight hoped the worst was over. "We both feel some relief," she told PEOPLE at the time. "It's gonna be more peaceful now." Sadly, peace has yet to break out. The couple, whose TLC show Jon & Kate Plus 8 is on hiatus until Aug. 3, are once again in the limelight, and tempers are flaring, thanks in part to Jon's recent behavior. Rather than grieving over the end of his 10-year marriage, Jon's recent actions—including a lavish trip to the French Riviera—resemble a carefree kid on summer break, complete with public displays of affection towards his new 22-year-old girlfriend, Hailey Glassman, the daughter of family friends. "Kate is just shocked by how he's been acting," says a source close to her. "He's throwing this new relationship in her face. It's like he's acting out, like this is supposed to be his revenge."

Not true, say Jon's friends. "He doesn't want to abandon Kate, but he's looking forward to putting the past behind him," says a longtime pal. According to another, "he's doing what anyone else would do: trying to get himself going in the right direction." Right now his destination is a two-bedroom apartment about 130 miles from the family's Wernersville, Pa., home. On July 18 Jon, 32, was spotted hauling his belongings, including a large flat-screen TV, into his new bachelor pad at a luxury building on Manhattan's Upper West Side. While the place certainly isn't large enough to accommodate his kids (Mady and Cara, 8, and 5-year-old sextuplets Aaden, Alexis, Collin, Hannah, Leah and Joel), the plan is for Jon to stay there whenever it is Kate's turn to take care of the kids back home. "I'm here off and on," Jon tells PEOPLE. "New York is great. I love it here."

Helping him decorate his new home? His girlfriend Hailey. "I'm highly influential on how it will look," Hailey says. "We both like modern-meets-Asian, red accents and plants, bamboo curtains so nobody can look in."

Meanwhile, Kate, 34, has been trying to avoid prying eyes as well, especially for the sake of her kids. On July 18 she and her brood were caught in the middle of an angry shoving match between security guards and paparazzi as they tried to enter a Manhattan studio for a TLC promotional event. (Jon arrived at the event after the shoving incident.) Kate and staffers ushered the kids out of harm's way—a routine that Kate, who turns around tabloid covers so her children won't see them, is familiar with these days. "The picture of her blocking the kids from the paparazzi, that's who she is: Mama Bear," says a friend.

Now her protectiveness includes shielding her children from the pain of seeing their dad with another woman. "Kate's been doing everything she can to make sure they don't hear about all this, and that they won't have their lives all messed up by it," says the source. That's proving to be a heady job, as Jon has happily posed for pictures with Hailey and was recently seen dining with a tabloid reporter. But so far the kids haven't been told about their dad's new girlfriend and, according to a source close to Hailey, there are no plans to introduce the sextuplets to her until after the divorce is final. (Hailey, whose dad performed Kate's tummy tuck in 2006, had met Mady and Cara in the past.)

Still, the couple are determined to defend their relationship publicly. "I love Jon and he loves me," Hailey tells PEOPLE exclusively. Hailey says she fell for Jon while he was nursing a broken heart at her family's home in New City, N.Y., in May. (Ironically, Kate recovered from her tummy tuck at the Glassman residence too.) "I thought, 'poor guy.' His heart was on the floor. He was sad; he was moping around. We started as friends and it grew." And how. After reporters flocked to her parents' house while Jon was staying there, "my parents sent me to my grandma's to get away," Hailey recalls. "At midnight he drove all the way there, a three-hour drive. He woke me up with a kiss on my forehead. He's one of the sweetest guys I've met."

But dating a Gosselin has its downside. "Going out now is stressful," Hailey says. "To say he has baggage is an understatement. But if we can make it through this, we can make it through anything." Hailey's determination may be the one thing she has in common with the last woman Jon loved. "For my kids, I've got to keep getting up, and I will," Kate told People in June. "I don't care how many times you knock me down, I will get up."