Hey there vampireknightzero! (; Well, me being a fan of A Song for XX, I think I've asked the same question before. I've been trying and trying to decipher the song but till today, I admit, I still can't understand it completely. It's just too emotional.
As Ayu had said, while she was writing ASFXX the words became so real. To my guessing, she wrote the song partly because of her dad's betrayal.
Anyway, my answer to why there was a change in lyrics - which I think you should just take as a personal view, is plainly due to mental characteristics.
She was pressed to create happy songs but ASFXX came in too emotional and devastating - that's why she couldn't be too direct saying things like: 'the more YOU said things like that..' but rather, blur things and make things seem more friendly like: 'the more PEOPLE AROUND said things like that..'
Yep, there was a change in lyrics but they were not meant to mean the same. Whenever she does lives, she gets very emotional thanks to her songs. That explains why she changes the lyrics some time or add in some other phrases.
I believe the 'anata ga' was meant to be the original lyrics instead of 'mawari ga' as she always perform the song with a change of lyrics. Yes, she was 'lying' in ASFXX for that phrase.
Whenever she does a live, she gets too emotional and it surfaces.
I just believe it was all due to her mental characteristics - that's all. I hope this does answer your question vampireknightzero.
Are u also a fan of Ayu's older songs? Your signature features a pic of her in her older lives right?
I hope I answered your question. Not a very good one, i know. D: