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For more than six years, Jennifer Aniston has been defined by her split from Brad Pitt and his insta-family with Angelina Jolie. But are her pity party-throwing days now behind her?

People magazine hints that the unlucky-in-love star's warp-speed romance with Justin Theroux could be the game-changer.

"She still strongly believes in marriage," a source tells the mag, "and has hopes she will spend the rest of her life with him."

Talk like that, coupled with rampant cohabitation reports, means that engagement and stork rumors should start any second now.

And expect those domestic blissed-out whispers to be set against the romantic backdrop of Hawaii, where Jen, 42, and Justin, who hits the big 4-0 on Aug. 10, have been vacationing in swanky rented digs since July 31.

"They are acting like regular tourists," a spy tells People mag, with another eyewitness adding, "They have been touring the island in a rented Jeep. ... Justin is beyond sweet and attentive to her."

On Monday, the pair turned up at the beachfront villa of pals (and sometime co-workers) Ben Stiller and Christine Taylor for a party celebrating Taylor's own 40th birthday.

"Jennifer hung out with Christine but never got too far from Justin," a source relays to Us Weekly. "They seemed to have a good time but didn't stay too long before they headed back to their house for the night."

A few hours earlier, Aniston and Theroux picked out a gift for the birthday girl at a local art gallery, a task they accomplished while apparently maintaining constant contact, including locking lips as the store staffer wrapped up their purchase (a pint-sized Buddha statue).

"They were the only people in the store and seemed extremely relaxed and happy. Jennifer was hugging Justin from behind," an onlooker tells Us. "When they left the store, Jennifer was massaging Justin's shoulders from behind, and he turned around and said something that made her laugh hysterically.

Sighs the bystander, "They seemed giddy in love and genuinely happy together."

And genuinely healthy.

On Tuesday, paparazzi caught Theroux picking up treats from a banana stand (cue "Arrested Development" joke here) as Aniston waited in the Jeep, and it appears they've kept up their fitness regimen during the tropical getaway.

"They have been jogging by their villa, and they are both in great shape," a spy observes to People, with another snitch telling Us, "Justin has a great body and working out is a big part of his life."


More on Jen and Justin's Hawaiian vacation

Jen bids farewell to Beverly Hills

Is Justin Theroux having a midlife crisis?

Jen introduces Justin to her dad