In beginning of The Distracted Preacher a maid is introduced in Newberry estate. It seems that both names refer to the same person and different spelling deals with different pronunciation. Quote:
A little girl crept in at the summons, and made tea for him. Her name, she said, was Marther Sarer, and she lived out there, nodding toward the road and village generally.
Next Quote:
Stockdale remained in some doubt till Martha Sarah came to clear the table. “Whose house is this, my little woman?” said he.
Another quote:
The minister stood up in acknowledgment of the honor. “I am afraid little Marther might not make you understand. What will you have for supper? There's cold rabbit, and there's a ham uncut.”