Mollie could possibly your Martha, but her information does not exactly match.
The 1900 Lamar County, AL Census - Sheet 151A, stated that Mollie was born April 1867. A marriage record was found for J. M. Simms and M. C. Watson on 8 Nov 1881 in Lamar County, AL, by a Minister of the Gospel.
Assuming the 1900 census birth date is correct, she would have only been 14 when she married Sims. If she had been married previously, she really would have been young.