Christina Green was on the student council of her elementary school, so on Saturday her mother’s friend thought she might enjoy seeing government in action: the local congresswoman meeting with constituents outside a supermarket near Christina’s home.

“I allowed her to go, thinking it would be an innocent thing,” said the girl’s mother, Roxanna Green, 45.

It did not turn out that way. A gunman shot Representative Gabrielle Giffords, leaving her in critical condition, and his fusillade killed six people, including Christina, a 9-year-old who loved animals and volunteered at a children’s charity.

She was born on Sept. 11, 2001, and she was proud of it, her mother said, because it lent a grace note of hope to that terrible day.

“It was an emotional time for everyone in the family, but Christina’s birth was a happy event and made the day bittersweet,” her mother said in a telephone interview from their Tucson home.

Christina, who was born when the family was living in West Grove, Pa., was one of the 50 “Faces of Hope” representing children from 50 states who were born on Sept. 11. Their images were printed in a book, with some of the proceeds going to a Sept. 11 charity.

“From the very beginning, she was an amazing child,” her mother said. “She was very bright, very mature, off the charts. She was the brightest thing that happened that day.”

Her mother, who grew up as Roxanna Segalini in the Bronx and Scarsdale, N.Y., is a registered nurse and has been a stay-at-home mother to Christina and her 11-year-old brother, Dallas.