Hi Sharon
I would not regard the DN of Botha as sufficient evidence alone
Eva died (according to secondary sources) 18/6/1878 but are not on the death notice of Keller who died 1877
She was mentioned on her fathers DN but are not mentioned in his will as far as I could see
IMHO an indication that she was not the natural child of Daniel Lourens Botha but I may be wrong of course
Link to Keller's DN:
https://www.familysearch.org/ark:/61903/3:1:3Q9M-CS92-DDHG?i=698&wc=Q6NX-R1S%3A1590242303&cc=2520237.