Nephi gives the immediate family. While it was a fairly common Hebrew practice to ignore women in texts unless they were central to them, this might not be the case here because Sariah is explicitly mentioned. However, she does have a role to play in the forthcoming story of the return for the brass plates, so that might be an explanation.
A possibility that there were other women in Lehi's family comes from a statement by Erastus Snow:
"Whoever has read the Book of Mormon carefully will have learned that the remnants of the house of Joseph dwelt upon the American continent; and that Lehi learned by searching the records of his fathers that were written upon the plates of brass, that he was of the lineage of Manasseh. The Prophet Joseph informed us that the record of Lehi was contained on the 116 pages that were first translated and subsequently stolen, and of which an abridgement is given us in the first Book of Nephi, which is the record of Nephi individually, he himself being of the lineage of Manasseh; but that Ishmael was of the lineage of Ephraim, and *that his sons married into Lehi's family* and Lehi's sons married Ishmael's daughters, thus fulfilling the words of Jacob upon Ephraim and Manasseh in the 48th chapter of Genesis, which says: "And let my name be named upon them, and the name of my fathers Abraham and Isaac; and let them grow into a multitude in the midst of the land." Thus these descendants of Manasseh and Ephraim grew together upon this American continent.... (Erastus Snow, Journal of Discourses 23:184-85, italics added)"
This may have been information available in the record of Lehi which Nephi simply does not mention.