Well she is a widow from her marriage to Seymour, if that was even finalized.

Anyway, D, I think what its meant by a disguise isnt in the typical sense of the word. After the whole Sin thing, people started flocking to Yuna for one reason or another. Most had only seen her at the stadium, and I think seeing her in different clothes would be more... oh, like a distraction (and not in the "OMG BOOBIES") way. People are going to recognize her, of course, but she'll probably be recognized less with the change of clothing. I dont think she wants to be completly unrecognizable, but she doesnt want to go places without being mobbed.