I believe Martha was married once before marrying George Carter. Here is the 1870 census:
1870 Census, Tarkington Prairie, Liberty County, TX:
Isaacs,Alfred 49 M W Farmer 1200 1000 MS Sarah 47 F W Housekeeping MS Elisha M. 18 M W TX Sarah 15F W TX Mary Jane 12F W TX Martha A. 10 F W TX William D.8 M W TX Betty Johnson3 F W TX Alfred W. Johnson 2 M W TX
Notice Martha is 10 years old.
Here is the 1880 Census:
1880 Dayton, Liberty County, TX census:
Alford ISAACKS Self M Male W 59 MS Farmer --- GA Sarah ISAACKS Wife M Female W 56 MS Keeping House MSMS Davis W. ISAACKS Son S Male W 16 TX Works On FarmMSMS Bettie ISAACKS Dau S Female W 14 TX At Home MS MS Alford ISAACKS Son S Male W 12 TX Works On Farm MS MS M. RAILEY Dau W Female W 20 TX At Home MS MS Tomie RAILEY GDau S Female W 3 TX MS TX
Notice M. Railey is listed as a daugher, 20 years old with a child Tomie.
There is only one M. that could be Alfred's daughter, Martha. The age is exactly right, 10 years difference between the 1870 and 1880 censuses.
I don't know what her first husbands first name may have been.
Do you have anything on a prior husband named Railey?