Hi Diana, you need a volunteer to look up the death cert in the WA Death Index microfilm (assuming she died in WA and not ID). Go to Random Acts Genealogical Kindness, www.raogk.org, choose Washington, choose Spokane County.
If that volunteer is tied up, you could contact the Eastern WA Gen. Soc., www.rootsweb.com/~waewgs/ to do the same lookup which they probably assess a reasonable fee. Once you get the death cert # you can order a copy from the State. Successful Hunting!