I'm not related - Been watching the progress- I think you're headed in the right direction with Lewis & Mila Wilburn as Celia's parents, also possibly Jacob and Delia/Delilah Gains Phipps on the Phipps side.
Found two other children who show parents of Tol/ Toliver Phipps and Celia Wilburn
James Phipps b. 1871 d 1935 Knox, KY and
Areva Bell Turner b. 1884? d. 1955 Bell, KY
Also found this -
1900 Knotts Fork, Knox, KY Phipps, Golbard/Tolbard, 63 b. Mar 37 KY KY KY md 30 yrs Cealia 47 b. May 53 KY KY TN mother of 8, 6 living Boyd 20 b. Jan 80 KY KY TN Lina 11 b. Mch 89 KY KY TN
Not sure these dates, birth places are reliable.
There seems to have been a lot of intermarriage between Phipps, Wilburn, and Hart families.