Maria was orphaned at the age of 7. At 18, she graduated from a teachers' college, then entered the abbey as a postulant. Three years later (age 21), she was sent to teach the youngest von Trapp daughter (the mother had died the year Maria entered the abbey), and eventually began taking care of the other children as well.
After about a year, the Captain, 25 years older than Maria, asked her to marry him. She did (she stated in her memoirs that she didn't love him, but learned to later) in November 1927. She bore their first child three months after the wedding. She later tried to alter that child's birth date to 1 year later, but official documents show otherwise. So, clearly, the master of the house was diddling the governess, knocked her up, and had to marry her.
7-8 years later (1935), the Captain lost his money, having transferred it from a stable London bank to a failing Austrian one run by a friend. When the money was gone, they rented out most of their house to students.
Maria didn't teach the children to sing; that was done by Franz Wasner, a priest and friend of the Captain. The family began singing at concerts to help bring money in to the impoverished family.
In 1938, the family moved to Italy (by train, not hiking over mountains), then sailed to the US in 1939, where they stayed.
No offense, but there are inaccuracies in this post as well.