Hi Debbie - at this point I would say that there may be more information at the Nacodoches county, Texas historical society, if they have one. I don't see a 1900 census for that area online, perhaps there is one. That would be helpful.
It seems that even though Minnesota might be Sadie's place of birth, more information could be found there to help you work backwards. Did she have siblings (obituary)
is there an obit or grave for the John B. Senasac who is hinted at marrying the widow Sarah L. Crisp after the death of Pierce Crisp in 1896? Those are questions that may still be answered in Texas. Was there an obit for Mrs. Crisp that might explain a 2nd marriage. Is there a marriage record for that Crisp-Senasac marriage in Nacodoches county? Probably after 1896, and before her death in 1917.
This website has some genealogy resources for Nacodoches County, Texas. Leave no stone unturned :)http://www.rootsweb.ancestry.com/~txnacogd/