I am not really surprised Raito got revived, afterall Kagura was still carrying and using his core. But Mimi's revival really came out of nowhere. Kind of invalidates one of the most emotional moments of this manga.
Ending Youmafication was always this easy? Just don't think about it.
It was a reality bending macguffin. Cattleya wanted to use to turn everyone into Youma. But I guess the ones who are already turned like the dragon widow will stay that way.
And Kagura already had Mimi's aramitama with herself as she used against the priest. Cattleya just conveniently could recreate herself two more times, so she decided to bring back those two.
Of course she could bring herself back, surrender, end youmification and atone for what she did and still bring back everyone who got turned into aramitama after recovering herself. But she would have to a responsible person and not the unstable lunatic that she even admits she is.