Michaela still detests the undead that have mastered the power of death, but she admires these humans with noble character. Even though they have fallen into the state of the undead, no one can deny their human identities when they willingly endure a thousand years of solitude and fight to protect humanity.
"What do you plan to do with these Undead Night Watchers?" Having understood the nature of the souls within these broken bodies of the undead, Muria took an opportunity to question Michaela. If his memory served him correctly, one of the conditions for angel reincarnation is the possession of a noble soul.
These night watchers undoubtedly met the criteria, but the sole issue is that they have degenerated into the undead—in the case of the youngest undead, it had been for eight hundred years already.