Ms. Bruce is listed as an "inmate" in the 1940 census. I have found mentions of a State Custodial School in Espanola Township - Spokane in the 1930s and an Eastern State Hospital in Espanola Township - Spokane as well as references to an asylum. It sounds like she was institutionalized at the time of the census.
"United States Census, 1940," Burness Bruce, Espanola Township, Spokane, Washington, United States
name: Burness Bruce
titles & terms:
event: Census
event year: 1940
event place: Espanola Township, Spokane, Washington, United States
gender: Female
age: 31
marital status: Single
race (original):
race (standardized): White
relationship to head of household (original):
relationship to head of household (standardized): Inmate
birthplace: Washington
estimated birth year: 1909
residence in 1935: Chelan, Washington
enumeration district number: 32-20
family number:
sheet number and letter: 9B
line number: 72
nara publication number: T627
nara roll number: 4362
digital folder number: 005460354
image number: 00335