The swearing-in ceremony was officiated by Riverside County Sheriff Stan Sniff. Dos Santos took her oath in a room full of other fellow officers.
"I so solemnly swear that I will support and defend and the constitution of the United States and the constitution of the state of California," Dos Santos said with her right hand raised.
The new deputy was also presented with her special badge to complete her officer's uniform. The ceremony was followed by the teenager's first ride in a patrol car with its lights and sirens on.
Dos Santos's mother said her daughter has been dreaming of becoming a member of law enforcement since she was seven years old.
"I just love helping people and knowing that you could go out there and help everybody is amazing," Dos Santo's told ABC7 Eyewitness News.
The teenager is credited with having a positive attitude for helping her tackle this potentially fatal disease.
"I got diagnosed last year, July 13, and I did chemo for three months and that's it. You just have to, you know, keep your hopes up. You can never think of the negative, always think of the positive," said Dos Santos.
Dos Santos displayed that same positive attitude at the Ben Clark Public Safety Training Center in Riverside. There she used what's called a Force Option simulator to test her reaction time to certain situations faced by deputies. She also proved to be a pretty good marksman.
The foundation that made the day possible for Dos Santos, the Debbie Chisholm Memorial Foundation, was founded by retired deputy Corky Bell.
"We've granted almost 400 wishes now, and spent about $1.3 million doing it," Bell said. "This is only the third child in the over 100 year history of this department we've sworn-in."
Later, the department's newest member was flown by Sheriff's helicopter back to her hometown of Temecula, where a barbeque was held in her honor. After lunch, Dos Santos was taken on a ride-along to patrol the streets of Temecula.