Doris Payne was found guilty last month of burglary and grand theft in connection with the January 2010 incident at the Fashion Valley shopping center Macy's.
San Diego County Superior Court Judge Frank Brown said Payne deserved the maximum sentence because she has several prior convictions for theft and has been sent to prison twice.
On Jan. 2, 2010, Payne approached the jewelry counter at Macy's, identified herself to a saleswoman as "Audrey," and said she was looking for a ring for her daughter, according to the San Diego Union Tribune. She managed to distract the saleswoman and exit the store with an $8,900 diamond ring.
Payne told a detective later that she sold the ring for $1,800.
Deputy District Attorney John Pro told the court that Payne has engaged in criminal activity for about 35 years and has gloated about it.
"She's made a lifelong career out of stealing and taking advantage of people," Pro said.
The judge dismissed a request by defense lawyer Gretchen von Helms to consider imposing a lesser prison term, possibly three years. Arguing that "there's more to her than her prior history," Von Helms pointed out that Payne had also devoted her life to raising two children and caring for her ailing mother.
Judge Brown conceded that Payne - a small, white-haired woman - has "a nice way about her, a nice manner," but said ultimately, "she's a thief."
When it was her turn to speak, Payne denied ever gloating about her past.
"To say I have no remorse, that's people who don't know me or people who think remorse is tears and lies," Payne said. "I have never gloated about stealing. I never saw anything to gloat about."
The Union Tribune said Payne could face extradition to Michigan, where she is accused of stealing a three-diamond ring from a Neiman Marcus in 1998.