She lost Heath Ledger four years ago, but Michelle Williams never moved on until she fell for Jason Segel. Michelle Williams and Jason Segel went largely unnoticed when they ducked into cozy Brooklyn restaurant Rucola just before 5 p.m. on March 25. Once she settled into her seat at the Italian eatery near her Boerum Hill home, the private actress let down her guard, unafraid to show a little affection with Segel. "Jason had his arm around her," says a source. Over a dinner of arugula salad and branzino, the pair chatted easily with four friends who joined them. And when the check came, the source adds, "Jason paid for the meal."

If anyone deserves a little chivalry and happiness, it's Williams. Since her ex-fiance, Heath Ledger, died of an accidental drug overdose in 2008, leaving behind daughter Matilda, now 6, Williams has been devastated. But now, the three-time Oscar nominee is finally moving on with Segel, 32. After years of platonic friendship, the two have turned up the heat, meeting up for several intimate dates in New York and L.A. Says a Segel source, "Romantically, this kind of happened overnight!"

But it was an arduous journey for Williams, who said that after Ledger died she felt like a "walking open wound." Says a Ledger source, "She was caught up in a big tornado, and she had a lot to recover from." Following several stalled post-Ledger relationships, the charming and quirky How I Met Your Mother funnyman won her over. "Jason is supersweet. He makes Michelle laugh and feel good about herself," says a Segel source. And perhaps most important to the single mom, 31, he's a pro with Matilda - he even took her for a scooter ride before the Rucola dinner date. No wonder Williams can barely contain her excitement: Says a source, "Michelle told one friend, "I love him!'"

More Than Pals

In recent months, Williams signaled she was ready to open her heart again. "Three years ago, it felt like we didn't have anything, and now my life - our life - has kind of repaired itself," she told Vogue last September. Perhaps taking that cue, Williams' best friend and constant red carpet companion, Busy Philipps, played matchmaker between the My Week With Marilyn star and Segel (whom Philipps has known since 1999, when they starred on the TV dramedy Freaks and Geeks). "Busy has been talking Jason up," says a source.

At West Hollywood's Chateau Marmont February 27, the threesome dined together before Philipps conspicuously left early, leaving Williams and Segel chatting for the next four hours. "Michelle and Jason had several glasses of wine and were both supergiggly," says a source. "He was trying to persuade her to go home with him. She was like, 'Oh, it's so late.' He was like, 'It's only 1 a.m.!'"

Since then, they have been spotted out on both coasts, having romantic dinners at West Hollywood's Comme Ca, and Frankies Spuntino in Brooklyn. And sources tell Us that when Segel was in New York in late March, he stayed at Williams' three-story brownstone and played house with the actress and Matilda. "Michelle doesn't do flings," says a Williams source. "Every person she gets involved with is someone she can entertain the possibility of spending the rest of her life with."

Opposites Attract

On the surface, the demure mom and the freewheeling bachelor seem like a head-scratching coupling. Russell Brand, of all people, once called the two-pack-a-day chain-smoker "a falcon among gulls when it comes to womanizing." And Segel, a puppet collector who cowrote 2011's The Muppets, bragged to Rolling Stone in 2009, "I like to drink, and I do."

But friends say Williams is drawn to Segel's sense of humor and kindness. "She finds him charming and romantic," says one source.

Even more promising, Segel - who hasn't had a steady girlfriend since splitting from actress Linda Cardellini in 2007 - has curbed his bad-boy habits. "He has made an effort to clean up his act," says a Segel insider. "Jason has been trying to be more of a grown-up lately. He is taking care of himself more, exercising, eating right and dressing better. Basically, not acting like a frat boy anymore."

Williams is in no small part to thank for that. "Michelle is the kind of girl he can bring home to his mom, so it all makes sense," continues the source. "She is classy."

So classy, in fact, he's nervous to introduce her to his pals. "A few weeks ago he said he wasn't sure he was ready for Michelle to hang out with his friends," says a Segel source. "He fears what might slip out about him and that it may be too soon. He's super into Michelle, and it just really seems like he doesn't want to mess this up."

Heath's Memory

And Williams could use a true romance. She and Ledger split in 2007 - four and a half months before he overdosed on a combination of prescription drugs - largely because of his escalating drug use, per -sources. Still, his passing "took a huge toll on her," says a Ledger friend. "It was an extremely dark period in her life. She is a romantic and always felt partly responsible for not being able to help Heath. It's weighed on her a lot."

Public finger-pointing from some of Ledger's friends didn't help. In a 2009 Vanity Fair cover story, Terry Gilliam, who directed Ledger in The Imaginarium of Doctor Parnassus, and cinematographer Nicola Pecorini blamed Williams, in part, for Ledger's death. Being away from Matilda "was really destroying Heath, really ripping at his heart," said Gilliam. Twisting the knife, Pecorini said Williams and Ledger had "nothing in common" in the first place. (Williams never publicly acknowledged their comments.)

Rather than shy away from Ledger's memory, Williams has made an effort to incorporate Matilda's dad into her life as much as possible: Photos of Ledger adorn her Brooklyn home, and Matilda still has the stuffed animals given to her by her dad, according to a profile in Vogue. Even Williams' pixie haircut is an homage to the late Australia native. "I cut it for the one straight man who has ever liked short hair, and I wear it in memorial of somebody who really loved it," she told British Elle last year.

During her most reflective moments, Williams recently confessed, she has even fantasized about a life with Ledger (who would have turned 33 April 4) if he were still alive. "It's one of my favorite things to imagine," she said tearfully. "It's actually one of my favorite places to visit."

False Starts

Nevertheless, Williams has tried to forge ahead. She and director Spike Jonze began dating the summer after Ledger died, but they broke up in 2009. She later admitted that their romance was ill-timed. "I thought falling in love again was the only thing that was going to save me from the pain," she said. "It just makes things more complicated." A source agrees that she wasn't in the right frame of mind: "When she met Spike, she was alone, sad and crying often."

Frustrated by her inability to move on, Williams nearly gave up on the idea of true love by contemplating a marriage to a platonic friend. "They didn't really have strong feelings for each other," says the Williams source. "It was so Matilda could have more stability and a father." She later explained to GQ that she put pressure on herself to find someone new so that she could give Matilda siblings close in age, "but I couldn't make that happen."

After scuttling her plan, Williams began dating again, but the guys were "a--holes who didn't treat her right," says another insider. She was briefly involved with Jane Eyre director Cary Fukunaga last spring, but "he didn't want to step up and be a stepfather to Matilda," says a source. "He was just looking for an unserious situation." And while filming Oz: The Great and Powerful last year in Pontiac, Michigan, Williams briefly got involved with a local cinematographer six years her junior but ended things when her feelings for Segel changed.
 

Real Deal?

Williams may be basking in the new romance, but Matilda remains her No. 1 priority. "She always puts Matilda first," says a Ledger source. And the L.A. based Segel, who one friend calls "a kid at heart," is winning points by making an effort to spend time with her and her daughter in their own neighborhood. "Jason has already showed her his commitment to her by canceling appointments to be with her and Matilda," says a Williams source. "He told her how much he likes Brooklyn. He plans on developing more projects, directing and writing more, allowing him to have more control of his schedule and do what he wants, and I think that gives her hope."

But can this pairing last? "Jason can be a bit of a playboy," says a Segel source. "The only way this will work is if he completely devotes himself to Michelle." For now, Williams is choosing to remain cautiously optimistic about the Five-Year Engagement star. "She doesn't want to repeat the same mistakes she made with Heath," says the Ledger source. "She wants a good guy who will give her a stable family life."

How Michelle Protects Matilda

Williams "will do whatever it takes to give Matilda as normal a life as possible," her friend, artist Dan Estabrook, once said. Indeed, the actress has eschewed Hollywood for a quiet neighborhood in Brooklyn, where she raises Matilda in relative privacy. (Williams also has a home in upstate New York, a small town with a population of 250!) "She's a very responsible parent," adds a source who worked with Williams on Oz: The Great and Powerful. "She wouldn't be pushed around schedule-wise when it came to commitments for Matilda."

(Us Weekly)