What I did was go to my local civil registry office and tell them what I wanted to do. They then asked me to write a submission which would be given to a judge who would then decide if I could legally change my name or not. I had to explain that nobody else would be affected by the change. Mine was refused with no chance of appeal and no reason was given.
But before your wife takes this step, think of some of the consequences. Any legal documents she has signed up to now would all have to be legally changed- bank accounts, escrituras, wills etc.