Final answer:
Maria Anna Mozart, also known as Nannerl, was the sister of Wolfgang Amadeus Mozart and was recognized as an accomplished pianist.
Step-by-step explanation:
Maria Anna Mozart, also known as Nannerl, was indeed the sister of Wolfgang Amadeus Mozart. She was an accomplished musician and is most recognized for her abilities as an accomplished pianist. While it is less known, she also played the violin. However, her abilities on the piano were particularly noted during the period, with reports that she was highly skilled and performed frequently. The correct answer to the question is that Maria Anna Mozart was both known as Nannerl and an accomplished pianist.