I believe that Harriet's father and brothers John and Joseph A were all living in Jackson County, IL at the time of the 1900 Census. Her father is most likely Abel P. Campbell born April 1850 or 1851 In Illinois. In 1900 A.P. Campbell is living with the Charles Wayman family in Sand Ridge, Jackson Co., IL listed as a boarder. Sons John (born August 1888) and Joseph (listed as J.A. born July 1875) are living with the William S. Wayman family, also in Sand Ridge. Charles and William Wayman are the sons of John Wayman, with whom Harriet was living in 1900. The Waymans all seem to come from Kentucky, and there is no apparent family connection to the Campbells.
In the 1880 Census of Carbondale, Jackson Co., IL, A.P. Campbell has wife Sarah J born 1848 Alabama and son Joseph A., born 1875, Illinois. This son Joseph is the one who is in Cass County, Texas in the 1910 Census with father A.P. Campbell. Joseph's wife and children are listed as though they are the sons and daughters of A.P., but the 1920 census for Sevier Co., Arkansas makes it clear that the "Mollie" from the 1910 census is Joseph's wife Mary and the others are her children from her marriage to Charles Elliott and her son with Joseph Campbell, also named Joseph.
There is an Illinois marriage for Abel Campbell and Sarah Taylor in Jackson County, IL for August 20, 1874.At Ancestry.com there is a Texas Death Certificate for Joseph A. Campbell that shows he was born July 2, 1875 in Murphysboro, Jackson County, IL and died April 25, 1935 in Plainview Texas. It lists his father as A.P. Campbell and his mother as Berry (no first name).
Ancestry also shows an Arkansas Death Certificate for Abe Campbell with a date of November 25, 1929 in Sevier County, Arkansas.
Abe/Abel/A.P. is most likely the son of Benjamin Stoors Campbell, born 1806 in Connecticut and Electa Louise Pier Campbell, born about 1812 in Vermont. Abel P Campbell, age 9 is listed with this family in the 1860 Census of Perry County, IL (very close to Jackson Co.). Also living with the family is Philates Pier, most likely Electa's father. You can find some of this family on findagrave for Perry County, IL.
Since both your Harriet and her brother Joseph believed their mother's maiden name was Berry and she was 26 when she married Abel Campbell there is probably a first marriage for her to a Taylor in either Illinois or Alabama.
Good Luck! Hopefully you can find some more concrete proof but I think this will point you in the right direction.