I think her maiden name may be Hill.
Daughter's death certificate is at www.seekingmichigan.org http://seekingmichigan.contentdm.oclc.org/cdm/singleitem/col...
Seekingmichigan does not have soundex search so I searched for her by last name Bull County of death Muskegon.
Also, Michigan vital records on www.familysearch.org
go to search page, scroll down to digitized collections, pick United States and then pick Michigan from left column. Michigan Death Certificate Index 1921-1952 A search for surname Kelly with father's first name Peter. Show's John W and Royal's death certificate also have Elizabeth Hill as mother.
Again, good luck