Hi Stella,

A death certificate wasn't required on a state-wide basis until 1907. I'm sure she died earlier than that.

A lot of counties kept death records prior to that date. I'd contact the Adams County Auditor's Office, wei.secstate.wa.gov/adams/Pages/abouttheauditorsoffice.aspx .
They don't mention old death records but they are the recording place for county records. Successful Searching!