[Aga-chan]

^Didn't ayu say in the All Night Nippon interview that "A Song for XX" is about her mother? I think she did. And she also said that people can put whatever they want in place for "XX". Maybe she wants the listeners to put as "XX" whatever they relate the song to.
As to her changing the lyrics of "A Song for XX", maybe she was too shy to address the person directly while writing the lyrics? Or maybe she did notice only afterwards that she wasn't talking about people around her, but this one particular person?

And I think saying things like "obviously" etc. isn't often appropriate. Because as long as we don't know what ayu herself thought or felt while making a song, we can only make assumptions. Maybe some songs were written about a particular person, but it has become universal afterwards. Just because she changes "you (kimi, anata)" to "you all (minna)" doesn't necessarily mean it was meant to be like this from the start. Otherwise she probably would have written "you all (minna)" to begin with, wouldn't she?