Courtney Wagner, 38, was arrested for cocaine and heroin possession after police responding to a report of a gunshot at her home allegedly found drugs there.
An unidentified male was arrested at the scene for negligent discharge of a firearm. No injuries were reported in the incident.
TMZ said Wagner will not face charges because police did not follow procedure.
"Deputies did not have probable cause, consent, nor a warrant to conduct the search and recover narcotics, so as a result the case is being rejected because of illegal search and seizure," the district attorney's office said in a statement issued to TMZ.
Courtney Wagner's mother, Natalie Wood, a star in "Miracle on 34th Street," "West Side Story," "Splendor in the Grass," "Gypsy" and other movies, died in November 1981. Her death at age 43 was ruled an accidental drowning during a boating trip with her husband and their friend, actor Christopher Walken.
Robert Wagner, 82, starred in the TV shows "It Takes a Thief," "Switch" and "Hart to Hart."