The sportswoman, who became a source of inspiration after surviving a near fatal crash last year, was due to share her experiences at a conference in the Spanish city titled 'What Really Matters'. Her autobiography Life is a Gift is due to be released on Monday.
CLICK ON PHOTOS TO ENLARGE
Maria's family released the following statement: "Dear friends, Maria has left us. She has had to go to heaven like all angels. We are thankful to God for the extra year and a half she gave us."
Leading the tributes from the world of Formula One was the test driver's Spanish colleague Fernando Alonso.
He said: "I had just taken off my crash helmet when they told me. I don’t know what to say. Pray for her, for her family and for the whole motorsport family. She was loved by everybody."
Maria almost lost her life in an accident last June while doing a test drive for Richard Branson’s British team Marussia at the Duxford Aerodrome ahead of the British Grand Prix.
But despite suffering serious head injuries and losing an eye in the impact, she recovered – and the whole experience had a life-changing effect on her.
Speaking exclusively to HELLO! magazine's sister publication HOLA! Maria said: "The accident has given me a new perspective about life, about the things that matter.
"It has taught me that to achieve what you want you have to educate yourself in sacrifice through effort.
"Now I have just one eye maybe I perceive more things than before. Before this, my life was a race against the clock, and now I see you have to stop and measure things in a different way."
Maria leaves behind her husband, 29-year-old personal trainer Rodrigo Garcia Millan, whom she wed in July and planned to start a family with.