"You can still move on and have the memories," a source close to the pop star tells PEOPLE, noting that Simpson, 25, still speaks to her soon-to-be-ex-husband, Nick Lachey, 32. "Nick will always be an important part of her life."
Also on the chain with her 3.5 carat bauble are two crosses – one that her parents gave to her, and another that is identical to a cross worn by both her sister, Ashlee and mother, Tina.
The jewelry pieces represent "a combination of things that are important to her," says the source.
As for the new main man in Simpson's life, the singer has turned to her pal and hairstylist Ken Pavés since her split from Lachey.
Pavés joined Simpson as she lobbied for Operation Smile in Washington, D.C., in March and again at an awards show in Australia in April.
There's a precedent for this platonic stylist-star relationship. Think Jennifer Aniston's postbreakup friendship with longtime stylist Chris McMillan; Kate Moss enlisting stylist James Brown for shopping and meals out after Pete Doherty; Gisele Bündchen partying with Harry Josh, even before the Leo breakup.