Cause of death will appear on the death cert. Order directly from the county of death clerks office.
Obits. usually say - after a long illness, etc..
TRY - Find a grave – FREE SITE - volunteer site all states; frequently has headstone pic
DO NOT SEARCH FOR A MARRIED WOMAN USING HER MAIDEN NAME.http://www.worldvitalrecords.com/
Try Vital Records – Birth, Marriage, & Death, Social Security Info., Census Records – FREE ALL STATEShttp://search.labs.familysearch.org/