Born in Silves in 1914. She was a Painting student at the Lisbon School of Fine Arts during the 1920s, where she met the architect and future husband Francisco Keil do Amaral. However, he did not complete the course, which he disagreed with due to the academic environment in which he practiced. 

His long artistic career covers various activities such as painting, drawing, ceramics, scenography, advertising, literature or illustration. In illustration, Keil became a reference at national level, in children's illustration that he began in the 40s. figurative generation practiced in the first decades of the 20th century, Maria Keil developed a creative discourse based on the stylization of drawing, always combined with reality.

 In November 2004, the National Library dedicated an exhibition to him that brought together works from over sixty years of activity.

He passed away on June 10, 2012, in Lisbon.