“servant.” The Hebrew word is amah (#0519 אָמָה), which refers to a woman who is not free in one sense or another, generally a female slave, but perhaps, for example, a concubine.
“the inheritance of God.” That is, the land that her family inherited when the land was divided by lot (Josh. 14-19, esp. Josh. 14:1-2). Thus, the land her family got was recognized as the family’s inheritance from God. If a family died out without anyone to inherit its allotment, then the land went back to other members of the tribe.