While Ben Affleck sat for interview after interview promoting his new film, Jersey Girl — and dishing on the Bennifer bust-up — Jennifer Lopez, 34, made a public statement of her own.

On March 8 in Miami, while dining on sushi at the Shore Club's Nobu, Lopez and her new leading man, Marc Anthony, 34, couldn't keep their hands, or their lips, off each other. (Interestingly, Lopez and Affleck publicly kicked off their romance with a liplock at Nobu in New York City in 2002.)

"They were making out in front of everyone," a witness tells Us. "It was impossible not to notice them."

In case there was any doubt, less than two months after her split from Affleck, 31, Lopez is making it clear she has moved on — and this time, it's final. A source tells Us that Lopez, in her ultimate farewell to the relationship, has decided to return her much-talked-about $2.5 million, 6.1-carat pink diamond Harry Winston engagement ring, closing the door on any possible reconciliation.

"She plans on quietly giving the ring back," a Lopez insider tells Us. "She's not doing this for the media. She's doing it for closure. It's the relationship's death certificate. He has demons that will never go away."

And yet, the actress — who has only communicated with Affleck via e-mail and letter since the split — isn't quite ready for a face-to-face meeting with her ex (she skipped the star-studded New York City premiere of Jersey Girl, in which she has a minor role as Affleck's doomed wife). A source tells Us now that she'll recruit a neutral intermediary to hand-deliver the bling. (It's not the kind of thing you'd UPS.) "The breakup is still really raw for her," the source says. "I wouldn't call them friends at this point." Is It Right?

So is Lopez doing the right thing? Etiquette experts say an ex-fiancée, no matter how jilted, is expected to return the ring. (Affleck, says a source, never asked for it back.)

"If a wedding is called off, she has to give back the ring," etiquette expert Peter Post, author of Essential Manners for Men, tells Us. "There isn't a good justification to keep it."

But surely there must be some leeway when the groom-to-be first carouses with strippers in Vancouver, then walks away from their relationship days after they postponed their $2 million wedding?

Certainly, few would have been surprised if Lopez had chosen to keep her cherished rock. If she were to sell it — say, for charity — experts estimate it would haul in a pretty penny.

"Because it has the Bennifer name attached to it, it would fetch above and beyond what it would go for at Harry Winston," says Constance White, style director at eBay, where Helene Eksterowicz's 2.78-carat engagement ring from The Bachelor's Aaron Buerge recently fetched $28,300. "It wouldn't be unreasonable to start the bidding at $1 million." Why Now?

It's possible she's upset that Affleck, on a blitz to promote his make-or-break role in Jersey Girl, has talked about their failed relationship to Rolling Stone and Dateline NBC and on Saturday Night Live (to name just a few). But those closest to Lopez — who waited years to discuss her P. Diddy relationship — insist it's just a sign that the world's most famous bride-to-be is ready to reinvent her life.

"She was shell-shocked, but now she's ready to move on," says a source close to the singer. "It takes time to mourn. But now she knows it's over."

To speed up the healing, Lopez has virtually abandoned Los Angeles (and the multimillion-dollar Beverly Hills estate she shared with Affleck) for Miami. While Affleck was preparing for his March 13 SNL gig, she and Anthony went shopping at Bal Harbour, a favorite retail haunt of hers in Miami.

J.Lo's public makeout with Anthony at Nobu aside, the two have been careful to avoid scenes (and photographers) together, and a source tells Us that Lopez recently fired her security staff because she feared press leaks about their romance.

A source tells Us that, to avoid scrutiny, the pair now spend most of their time at Lopez's Miami Beach mansion, where they stay up until 4 or 5 a.m. watching TV or DVDs.

"Jennifer loves to sit at the pool for hours and soak in the sun," an inside source tells Us. "She wears a bikini and he wears cut-off jeans and no shirt. They lie around the pool kissing and laughing." Not that she has gotten lazy. Lopez, who starts filming Monster in Law with Jane Fonda in May, often works out twice a day, doing ashtanga power yoga and interval training to burn off the post-breakup weight gain she (and Affleck) suffered, a source tells Us. Lopez has even been spotted jogging up and down the road in front of her house.

Affleck, for his part, lately seems to be adjusting to his post-Lopez life with aplomb. On March 6 in New York City, he spent the evening surrounded by a group of women at the nightspot G2. Now What?

"He didn't talk about J. Lo at all," a source says. Adds an eyewitness, "He was the perfect gentleman." And after his SNL gig, regarded by many as a hit, he attended the cast party with a posse of about 15 guys at Ruth's Chris Steak House until around 3:30 a.m.

"Oh, we're all laughing," said Diane Sawyer, after watching an SNL clip two days later on Good Morning America. "I guess he laughs 'til it hurts."

As for Anthony, is he more than a rebound romance? After all, his estranged wife, Dayanara Torres, 29, still lives in Miami with their two young children — and a prolonged relationship with Lopez could complicate their ongoing divorce proceedings. (Even stranger, Anthony, by some accounts, is wearing a ring on his left hand.)

Still, sources close to Lopez aren't ruling out a long-term love connection. "J. Lo wants a family," says one source. "And she has a history with Marc. We'll see."

With reporting by Zoe Alexander, Jennifer O'Neill, Ryan Pienciak & Shelley Reinstein in New York City; Ken Baker in Los Angeles; Jed Dreben & Linda Marx in Miami