Jensen was in a crosswalk at the intersection of Grant Street and O'Hara Avenue around 8:15 a.m. when she was hit by a car driven by a 43-year-old man.
Jensen, a Brentwood resident, was taken to Sutter Delta Medical Center in Antioch, where she was pronounced dead.
Police said the driver, whose car came to rest against a sound wall after hitting a curb and a fire hydrant, was determined to be driving under the influence of a controlled substance.
A girl riding in the car suffered minor injuries in the collision but did not require medical care, according to police.
The driver, whose name has not yet been released, was arrested on suspicion of vehicular manslaughter, DUI resulting in injury, child endangerment and drug offenses. He was taken to county jail in Martinez.
Police are asking anyone with information about the collision to call Brentwood police Detective Justin Luo (925) 778-2441 or (925) 634-6911.