According to Family Search, her parents were:
Their dates for Martha's information are off just slightly from what you have listed, so I'd review what they have to see if there are any adjustments you feel are appropriate. Sometimes they have good data - other times... not so much.
Geni does not list parents, but does include a number of clues towards other sites that might have additional information:
My Heritage seems to agree with the parents in Family Search:
Rootsweb is showing a few inconsistencies. That's not unusual, but it's enough to take a closer look at the data:
These two seem to indicate that the mother's maiden name was "Norman". Seems logical, considering the name of the son, who is also listed in the Family Search records.
And yet another researcher shows her LNAB to be Duke:
Guess it depends on who you believe with this type of data.