I thought that morgana, who rejected her celestial origins was less close to the manifestation of justice.
But with the new lore and the Q and A, I think that morgana is as much "justice" as kayle, but in a different way.
What I mean is that although she rejects this power, her actions demonstrate that she is still acting for justice, in her own way. Thus, morgana, while rejecting her destiny, acts nevertheless unconsciously as an aspect of justice. Her mind rejects this, but she is constrained by her celestial nature to do justice.
This explains that she has as many wings as kayle, because she too represents justice.
Please Riot, tell me I'm right!
(sorry for my bad english)