Two entries with the name Martha.
Martha
The daughter of King Frion of Dessemoume.
She was kidnapped by a pack of thieves but was rescued by Lancelot. Frion wanted to marry her to Lancelot, but he refused and departed. Martha later bore Lancelot’s son.
Source
Les Merveilles de Rigomer | Jehan, mid to late 13th century
Martha
Daughter of King Irion and the wife of Tristan’s son Ysaie the Sad and had a son named Marc.
Source
Ysaïe le Triste | Late 14th century or early 15th century