I think Yasu, or Sayo as I prefer to call her nowadays, was always meant to be good-looking, both as a girl and a boy, despite her self-esteem issues. After all, she’s had no less than three Ushiromiyas fall in love with her, two of which (Jessica and George) were interested in her at first sight. Also, it was said that she looks a lot like her mother, who was a picture-perfect Italian beauty, and her father Kinzo wasn’t bad-looking either (Kinzo looks like Battler, and Battler is bloody popular with the ladies).
Now, I’m not saying this in any way to make Sayo’s pain from watching her “pathetic Yasu face” in the mirror any less real. In fact, I think having a further exacerbated Sayo’s issues in the long run. No matter who she falls in love with, she can’t help feeling that she’s tricking them with a pretty face hiding the “ugliness” of her body and her internal issues. It’s pretty sad.