Complex sentence: Fallin was the second woman elected to the United States Congress from Oklahoma; the first was Alice Mary Robertson, elected to Congress in 1921; she served for one term from 1921 to 1923.
Split into simpler sentences: Fallin was the second woman elected to the United States Congress from Oklahoma. The first was Alice Mary Robertson, elected to Congress in 1921, who served for one term from 1921 to 1923.