Her mother had a brief affair with Mr. Grim, and after finding out she was pregnant, he high-tailed it. Santana grew up in a trailer park, completely content playing with the other kids and little monsters who lived there, she never knew that there was anything considered better. Soon she graduated junior high and came to Monster High, where she realized that other monsters would look down on her. Now she keeps her home life to herself almost completely.
She works at a diner near her house where they require the waitresses to wear roller skates. She thought this would be a pain, but she ended up really enjoying it (the skating, not the waiting!) and since has wanted to join a roller derby team, but there are none in the area. Because she resents school and tries to stay as far away from it as possible, she had never considered the idea of joining an after school activity, but Ripper Grimm came up with the idea to start a Roller Derby Team sponsored by the school, and Mars was in!
Since she grew up around trailers, and a technically-challenged mother, she learned lots about mechanics from her neighbors who helped her when their trailer had problems. She soon found the world of motorcycle racing through a friend, and saved up her money to buy a broken bike. She restored it, modified it, and races it at night and on the weekends when ever she can. She takes great pride in her chopper, (named Buddy, after her celebrity crush, Buddy Holly) and treats it like many would their pet.
She really enjoys her life, and thinks that overachievers and wealthy people are the poor ones, because she has a mother and friends that love her, and considers her priorities to be straight.