Don't know if this will help you or confuse you to death.
Looks like Susan Erskins Newman married after death of Joel.
Spencer County, Indiana
Index to Marriage Record 1850 - 1920
County: Spencer
Name: Susan A Newman
Spouse: William Harp
Marriage Date: 05 Mar 1863
Book: 4
Original Source Page: 537
Now the confusing part. This William or another William Harp
married the below:
1-County: Spencer
Name: William Harp
Spouse: Edna Erskins
Marriage Date: 17 Jan 1866
Book: 5
Original Source Page: 234
2-County: Spencer
Name: William Harp
Spouse: Nancy F Erskines
Marriage Date: 31 Mar 1870
Book: 6
Original Source Page: 156
3-County: Spencer
Name: William Harp
Spouse: Sarah E Moore
Marriage Date: 21 Dec 1873
Book: 6
Original Source Page: 540
The only Harp in the 1870 Census for Spencer County is:
Harp, William 30 m farmer KY
N. Frances 23 f hkpr KY
Mary 6 f IN
Nancy 4 f IN
Emma 2 f IN
William 8/12 m IN
Erskin, Rila 21 f KY
Roberta 10 f IN
I couldn't find a burial for Susan Newman or Susan Harp.
I did find this burial, just in case you need it
Bluff Cemetery, Huff Twp., Spencer Co., IN
Mary Ann Newman
29 Mar 1856
w/o Joel
35y5m16d
Good luck with this one, your going to need it
James