I mean let look at it this way, Kaguya is sealed in the moon with no way to learn what she done is wrong, Madara learned what he did was wrong. Had Kaguya been sealed into Madara that means that Madara could still be alive, since Madara changed then surely Kaguya could change.
Orochimaru changed thanks to Sasuke and Kabuto, so I see no reason why Kaguya can't change.
Orochimaru changed thanks to Sasuke and Kabuto, so I see no reason why Kaguya can't change.