I agree with Allie, it looks like stress barring to me as well

The outer edges are the first parts of the feather to develop, so it would make sense that it occurred when she was at the start of a molt and the feathers were just beginning to develop. The pattern is different than a sf spangle markings since only the very edges of some feathers are effected.

Is this your bird, or photos you found online?
She looks to be quite mature, and in the process of or just finished breeding given that you can see her brood patch on her belly