The girl's mother, Rocquell Love, told the Las Vegas Review-Journal that the family initially planned to spend the holiday with church friends, but Love opted to send her daughter with a group of cousins under the care of an aunt after her 6-year-old son got sick.
Sgt. Richard Strader said the girl's uncle and cousins were standing only feet away from her when the car ran into her. By late Wednesday, friends and relatives had decorated the pedestrian street with bouquets of roses, teddy bears and cards in memory of the girl.
"It was a tragic, traffic scene," Strader said. "The odds are against people when they are out and about, unfortunately."
A witness to the accident, 15-year-old Aaron Francois, was trick-or-treating with his brother when he saw the 2009 Mazda RX-8 hit the girl. The car appeared to be traveling much faster than the 25 mph speed limit in the residential neighborhood.
Francois told the Review-Journal he heard a young boy scream, "That's my cousin, that's my cousin!"
The 41-year-old driver, Justin Caramanica, was arrested on a felony drunken driving charge and was being held at the Clark County jail. A court hearing has been scheduled for early Thursday morning.
Love said by the time she arrived at the hospital Monday night, her daughter was already dead.
She said she doesn't blame her sister for her daughter's death.
"She feels because she was with her, she should have been able to take care of her and protect her," Love told the Review-Journal.
Faith, a seventh-grader, especially loved books about Native Americans, and based her Native American princess costume on her readings.
"You know how most kids hide in the bathroom, supposed to be getting ready for school, but they're playing video games and texting?" her mother said. "My child would literally go in there with a book. She would read three or four books at a time. She just loved knowing things and learning."