Dear Mr. Erlam,
Thank you for posting your request on History Hub!
The state of Idaho began recording deaths statewide officially in 1911. We suggest you contact the Idaho Department of Health & Welfare to request a copy of the death certificate for Edna Beatrice Phillips. There is a State of Idaho Death Index compiled by BYU Idaho Special Collections that you should search first. We also suggest reviewing the FamilySearch wiki How to Find Idaho Death Records for additional information and/or resources for how to obtain her recorded death information.
You may wish to search the Idaho State Archives Native American Boarding Schools and Lapwai History websites for background information about the sanitorium in Lapwai, Idaho.
We Hope this is helpful. Best of luck with your research!