I cannot quite remember the scene from the Rabona/Agatha chap where Galatea tells Miria about her eyes, as I remember it she might actually have implied that it WAS an injury she recieved in a fight and then choose NOT to heal. But that's arguing semantics, the bottom line is she indeed remained blind willingly. And surely she did it to better hide from the ORG's trackers and the MIBs but I always figured there was also a psychological aspect to it that nicely adds to her character:
The motif of blinding yourself or gauging your own eyes out is a recurrent one in literature, beginning with things as old as Sophocles' Oedipus Rex, where Oedipus blinds himself after learning that he unknowingly killed his own father and commited incest with his mother. It is often assosciated with a feeling of guilt and self-punishment in light of fully realizing the extent of ones own failures and/or sins which I feel makes a lot of sense with Galatea:
Not that she commited any particular atrocities she should feel guilty about but one might say her sin is that of
not acting despite better knowledge: Due to her rank and her particular skillset she was one of the few warriors who were in the priviledged position of gaining a deeper insight into the inner workings of the ORG and the goals, attitudes, and methods of the MIBs. Miria had to do quite some digging to doublecheck on the info Rubel leaked to her, Galatea, being both highrank single-digit AND the Eye could have gotten half of that much easier, without somebody like Rubel nudging her in the right direction in the first place - all she needed to do was look at things 'with open eyes'. However she choose not to, or at the very least for a long time might have pretended to be "blind" to the truth.
Sure, she did her little deeds of good will like letting Clare and Jean go, but she did not act in earnest with regard to Pieta i.e. Later,she chose a life of hiding rather than opposing the ORG. She might be doing something good for the kids in Rabona, but in essence it is rather the kids giving solace to HER than vice versa...
In that conversation with Miria (M: if this were a normal warrior team, you would be the leader - G:No I am not like you, you do it) you have a feeling that she has changed quite a bit from her earlier high and migthy attitude and is actually suffering from quite a bit of self-remorse and -loathing, depression even. It was done with a bit of pathos there, but I do believe her when she stated that she planned on drawing in some Claymores to assist against Agatha to help the city, and then, once that was done die either mid-fight or by the ORG's hands. Cause she kinda had given up on herself I guess. I always saw the blinding herself in that way, too...
edit: btw it was nicely done by Yagi how you could feel how she found back to her old snidy cynic self through fighting again after all that time, that panel with her smiling wildly how things never go as planed was so awesome, there goes her arm tumbling down the roof and Agatha is all "haha now you're going down for good" and all she does is smile and say "hey so what, shit happens, now, come at me, bitch" (slightly paraphrasing here

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edit2: *SIGH* I just love her. I refuse to believe this mess will end without more goddess gala !!!