Complex sentence: She previously served as the 52nd Speaker of the United States House of Representatives from 2007 to 2011, the only woman to do so, and is to date the highest-ranking female politician in American history.
Split into simpler sentences: She previously served as the 52nd House Speaker from 2007 to 2011, the only woman to do so. She is also, to date, the highest-ranking female politician in American history.