The book I compiled from courthouse records contains marriages from 1824 to 1855.
The woman you seek is Elva not Eva. She was Elva on 1880 census and Elva on gravestone.
Her married name was O'Neil on gravestone not O'Neal. See photo here.
http://www.findagrave.com/cgi-bin/fg.cgi?page=gr&GSln=o&...;
I found a marriage record on FamilySearch.org. Elva C Heed married John O'Neil, age 32, in Dover, Morris County, NJ on 5 June 1894.
This couple was living in Philipsburg in the 1895 census on Ancestry.
They had a child on 10 Sept 1895 in Philipsburg, Warren Co. (FamilySearch)
Elva C. O'Niel (sic) died 22 July 1899 in Belvidere. (FamilySearch)
The Belvidere newspaper carried an obit on 28 July 1899, page 3, col 4. You can order a copy from the Warren County Library here
http://www.youseemore.com/warrencl/contentpages.asp?loc=18If there is anything else I can do to help, please let me know.
Sharon Meeker