Confederate veterans and their widows were dependent upon the generosity of the already impoverished former Confederate states for any postwar pension benefits. In awarding pensions for Confederate service, Texas, like most other southern states, confined its relief payments to veterans or their widows resident in Texas since 1880 who were disabled or indigent. Therefore, the index of applicants for Confederate pensions in no way represents a complete roster of Texas residents who fought for the Confederacy.
https://www.tsl.state.tx.us/arc/pensions/introcpi.html

Additionally, the Tennessee State Pension Commissioners rejected any applicant who had sworn allegiance to the United States prior to Lee's surrender, April 9, 1865. I believe this is also applicable to membership in the United Daughter's of the Confederacy (UDC)