Complex sentence: Cuoco has a sister, Briana, who is a dancer and currently made appearances on the online web series "The Lizzie Bennet Diaries" as Mary Bennet until it's end in March of 2013.
Split into simpler sentences: Cuoco has a sister, Briana, who is a dancer. Briana made appearances on the online web series "The Lizzie Bennet Diaries" as Mary Bennet until the series end in March of 2013.