According to her Wikipedia article, she was Holy Roman Empress from 1648 to when she died in childbirth in 1649 at the age of 17. She was the daughter of Claudia de Medici. Her maternal grandparents were Ferdinando I de' Medici, Grand Duke of Tuscany and his wife Princess Christina of Lorraine.
From history-of-fashion.tumblr.com/post/141359404634/1648-unknown-artist-portrait-of-maria-leopoldine; enlarged one quarter. Also posted to the “Casual” Dress Album here.