Complex sentence: Authorities then placed her in another foster home, where she did fairly well, but in mid-December 1977 the arrangement very suddenly collapsed, so through the end of that month into early January Genie lived in a temporary setting before moving into another foster home.
Split into simpler sentences: Authorities then placed Genie in another foster home, where she did fairly well, but in mid-December 1977 the arrangement very suddenly collapsed. Through the end of that month into early January, Genie lived in a temporary setting before moving into another foster home.