Is this your Mary (Mollie is a nickname for Mary); and her mother Nancy who has remarried?
1880 census Uvalde, Uvalde Co, TX:
Category: Name;Relationship to head of household; Marital Status; Gender; Race; Age; Birthplace; Occupation; Father's Birthplace; Mother's Birthplace.
John B. GOODMANSelfMMaleW65TNStone MasonMDVA Nancy GOODMANWifeMFemaleW34LAKeeping HouseLALA Marmaduke GOODMANSonSMaleW8TXTNLA Luwenia B. GOODMANDauSFemaleW6TXTNLA William P. GOODMANSonSMaleW4TXTNLA Algeman GOODMANSonSMaleW2TXTNLA David M. GOODMANSonSMaleW1TXTNLA Mollie J. WALKERSDauSFemaleW15TXAt HomeMSLA Rebecca COOKDauWFemaleW17TXWasher WomanTNLA
I would check for marriage records in Gonzales Co, TX, see if Nancy used her maiden name, or her married name from previous marriage.It might be a beginning.
If this is your Nancy, have you tracked down any of the descendants from this second marriage, see if any of them know anything about Nancy and her first husband?For a sample Marmaduke Goodman is in Bexar Co, TX in 1900, I didn't follow him anymore then that.
Do you know when and where Mary died?A copy of her death certificate should show the names of her parents, including her mother's maiden name, if the informant had that knowledge.