Specialist Ciara Durkin was discovered, with a single gunshot wound to her head, in a secure area of Bagram Airfield last month.
On Saturday the 30-year-old, born in Ireland and raised in the United States, was buried with full military honors. Durkin was promoted posthumously to corporal.
Residents held flags in silent tribute to the fallen hometown soldier.
Joe Brill of Quincy said, "The least we could do is thank this young woman for giving her life and serving our country," CBS Station WBZ reported.
The service held at St. John the Baptist Church in Quincy was also attended by Governor Deval Patrick and Senator John Kerry.
Her brother Pierce delivered a eulogy, recalling his sister's selflessness and ready smile. Her large family sat next to her flag-draped coffin.
Writing from Afghanistan, Durkin's commander said her loss "creates a hole in our hearts and our formation."
"Corporal Durkin's unparalleled devotion to duty, attention to detail and selfless service contributed significantly to the success of the mission," said Marine veteran Frank Downes.
Durkin was remembered by Major General Joseph Carter, Adjutant General of the Massachusetts National Guard, for the way she cared for fellow soldiers. Carter also recalled her commitment to her mission.
She had joined the Army National Guard in October 2005 after getting laid off from her information technology job. Her duties included making sure the finances of soldiers were in order and that their families were getting benefits.
The death of Durkin, who was found dead within the confines of a secure air base on September 28, were made more mysterious by news she told her family while visiting home three weeks before she was killed. Durkin's said Ciara told her she had "discovered some things I don't like and I made some enemies because of it," and asked if anything happened to her, to make sure it was investigated.
Her family initially complained that military officials told them she was killed "in action," but then later said she died in a "non-combat related incident."
Durkin's family met with Army investigators this week and were reassured everything was being done in the investigation. The family discounts the possibility of suicide.