Ruas was born on 5 January 1948, in Lins, São Paulo. She became interested in mathematics through a junior high school mathematics teacher, Râmisa Jorge,^[1] and after entering university study in 1967,^[2] earned a licenciate in mathematics in 1970 through what is now the Faculty of Science and Letters of the Araraquara campus of São Paulo State University.^[1][2]

She became a teaching assistant at the same campus in 1971,^[1] while at the same time studying for a master's degree at the University of São Paulo, working there with Gilberto Francisco Loibel; she completed her degree in 1974,^[1][2] and was promoted to assistant professor. In 1982 she moved to the University of São Paulo as a professor.^[1] She defended her doctoral dissertation, Finity Determinacy and Applications at the University of São Paulo in 1983. It was jointly advised by Luiz Antonio Fávaro and Terence Gaffney.^[1][2][3]

She has headed the mathematics department at the University of São Paulo, was a founding member of the Brazilian Mathematical Society, and has organized the biennial Workshop on Real and Complex Singularities in Brazil.^[1] She is a coauthor of the book Differential Geometry from a Singularity Theory Viewpoint (World Scientific, 2016, with Shyuichi Izumiya, Maria del Carmen Romero Fuster, and Farid Tari).^[4]

Ruas is a member of the Brazilian Academy of Sciences, elected in 2008,^[1][2] and in 2009 was named a commander in the National Order of Scientific Merit.^[2]