Complex sentence: She is serving in her second term and is Delaware's first female governor, as well as the nation's oldest serving governor, and, since January 2008, the longest-serving female governor in U.S. history.
Split into simpler sentences: She is serving in her second term and is Delaware's first female governor, as well as the nation's oldest serving governor. Since January 2008 is the longest-serving female governor in U.S. history.