What made Hildegard's songs different from simple chants that were common at the time?

While most plainchant was composed anonymously, Hildegard was an exception. She also authored texts on various subjects ranging from medicine to spiritual revelations which were later approved by church authorities. Hildegard is a fascinating historical figure so the bulk of the Wikipedia article on the medieval composer and abbess is presented below and a careful reading of the entire article is recommended. That said, the most important sections for your study are Introduction and Music.

answer: 25.8 years old or 25 years old

the answer is the government.