Yes, Idaho is restrictive on their release of records but 50 years after a death and if you meet the criteria, you should be able to order a copy of her death certificate.
Go to the Clearwater County Auditor, Recorder and Clerk of the District Court web site, clearwatercounty.org/?Auditor1 for contact info.
The Idaho Genealogical Society, 208-384-0542 might also have this info.
Contact the Clearwater Public Library, manta.com/c/mmcr87b/clearwater-public-library about requesting a copy of her obituary and any death article. Successful Searching!