Sariah begins to complain to Lehi because of her fears for them--that they had "perished in the wilderness". She even went so far as to complain about Lehi's visions being the reason for their suffering and that these visions would be the cause of all their deaths.
I love that about the Book of Mormon. The Bible and the Book of Mormon narratives tend to focus on the events from a man's point of view. That's just the way things were in that age. However, the authors of the Book of Mormon do give more insight into the thoughts and emotions of women of God (warts and all) than we find in the same comparative proportion in the Bible. I believe this is because the overarching theme of the book is that it is principally about families and how they and their descendants fared in a new land. It makes sense, then, that more focus is given to women in this book, for they bore the sons and daughters of this new civilization.
Lehi, instead of breaking out in indignant, patriarchal rage, comforts her by encouraging her to look back on those times when she did believe in the visions and the land of promise that they were going to eventually inherit. This is a good model for any father and husband to follow when times get tough.
Verses 7-8 give us a sense of the comfort Sariah must have felt upon the return of her four sons.
After offering sacrifices and burnt offerings (which indicates they must have traveled more than three days' journey from Jerusalem according to Mosaic law as it was interpreted at that time), Lehi examines the plates and discovers that they contained the five books of Moses, a record of the Jews from the beginning "even down to the commencement of the reign of Zedekiah, king of Judah" (Lehi's day) and many prophecies.
But what seems to have most intrigued Lehi was learning that the genealogy of his own fathers, of the tribe of Joseph, was inscribed on the plates. He now had confirmation that he was of the lineage of Joseph of Egypt. This is an important thing to remember as you read the rest of the book, for it shows how the Lord remembers His covenant with Israel, even as He allows them, through their agency and bad choices, to scatter themselves to all ends of the earth. He commands there to be records kept of the migrations of those tribes. We have had that record in the Old Testament for the tribe of Judah and now we have it for the tribe of Joseph. How many other tribes kept records? The Book of Mormon tells us that there are many. And, they have kept records and were visited by Christ.
It's no wonder Nephi records:
21 And we had obtained the records which the Lord had commanded us, and searched them and found that they were desirable; yea, even of great aworth unto us, insomuch that we could bpreserve the commandments of the Lord unto our children.