It is clear that Kit is no longer in Algeria. Tessalit is on the border of Mali and Algeria but the references to the sea mean that present day Mali (then French Sudan) cannot be Kit's location.
She is likely to be either in Senegal or Mauritania - both part of French West Africa or Afrique Occidentale Francaise (A.O.F.), as it was known. A.O.F was a federation of eight French colonial territories: Mauritania, Senegal, French Sudan (now Mali), French Guinea (now Guinea), Côte d'Ivoire (Ivory Coast), Upper Volta (now Burkina Faso), Dahomey (now Benin) and Niger. The federation was formed of individual coastal colonies the French had first seized as trading posts in the 17th and 18th centuries. A later reference to the advice of the Consul at Dakar (p249) makes Senegal the most likely location for Kit's wherabouts.