Well, I'm in Catalonia, but for that matter it's the same.
There are lots of women here named
Maria, but there are also LOTS of women with a double name, and it is usually
Maria something. And mostly, or they go for both, or they go by the second. That's why most Maria-something have shortened it to Mª and the other name!
For example: my mother is
Maria Teresa, and my aunt,
Maria Pilar. But only my grand-parents or very close family call them by the whole name, they go mostly by
Teresa or Teia, my mom, and
Pilar my aunt.
Weird thing, really!
Eva