Ultimately the only person that can explain her behavior is the woman concerned. As has been said she may not see it as any big deal about dropping by unnanouced BUT some cultures do not like that. I would have thought that as she has lived in Spain for quite a few years I would have expected for her to know what the etiquette dictates. I left my country of birth nearly 20 years ago & not everything is accepted as easily here as it was 'at home" for me. Now when all is said & done & with the greatest respect after knowing her for 3 years this is not a great sign. These are questions that after this length of time you should already know the answers to. If it were me my mind would be working overtime trying to figure out what was going on & if I could make no progress after this length of time I would be walking away! Perhaps (& again I am not saying this with any disrespect) BUT if you don't (or cannot get understand it/fix it) then what else do you not know about which leads to a lack of trust etc. If you cannot talk & understand ( you do not have to agree with everything) whats going on with her etc then IMHO perhaps you should walk away & stop beating yourself up over it!
Well, I do not know the reason for this issue because my mother does not want me to find out. Her health is not good and she can´t go out without someone to aid her walk. For her, as much as she too would like our friend to call, she accepts her because otherwise she would lose someone she values.
As for knowing why, you´re right, I should by now, but our friend is hard to know and is only now just starting to tell us more about herself - the little info I shared with you all. Also, living in a kratocracy has made us think a little too much with our hearts some times.
I am respecting the wishes of my mother and erring on the side of caution on behalf of my friend by bringing this topic up here. What we are going to do though, is not open the door when we are not expecting anyone, i.e. the postman, a friend who has called ahead of time. This is the most practical and effective solution, really.
Now, if we could please focus on the reason for why my friend has not accepted the fact that people in my country generally prefer others to let them know in advance that they would like to come beforehand, after living here for more than ten years, it would help stimulate the discussion further.