Yes, I read that part several times but it is extremely unlike that someone obtains a doctorate at the age of 22; 4 years after finishing high school. And afterwards goes on to pursue her master's degree... So, the thesis was most likely a Bachelor thesis (which might have had a slightly different name; or could even have been a combined 'Bachelor/Master'-degree; which would be a 'doctorandus' in the Netherlands; meaning that you have qualified to start a trajectory towards a doctorate).
I think you are right; so, the Spanish publication incorrectly calls her a doctor.
It happened to me once as well at the very first conference I attended; when they thought I had two doctorates (as my title was 'drs.') while I had just started to pursue my PhD.
This confirms that her first degree was indeed a Bachelor's (or probably the Italian equivalent at that time - causing the confusion).
Found some more information that might be relevant on
Wikipedia. Apparently, those with a master's degree are called 'dottore' in Italy...