The maid has reportedly admitted she used a kitchen knife to kill Tala al-Shahri, Gulf News reported. No motive for the killing has been mentioned.
The girl's parents were at work at the time and her sisters were at school.
The girl's father, Khalid al-Shahri, rushed home after hearing of the attack, and on the way, caused an accident that killed two people, Gulf News said.
The girl's father said his family never mistreated the woman.
"My wife and daughters have never ill-treated her and she had no plans to leave us one week before the murder was committed. She did not have the intention to travel home and we would not have objected to it, anyway," he said.
The family of the victim was in court when the trial began.
The prosecution is expected to ask for the death penalty, Gulf News said.