I have Cass as a follower. I nuked the NCR and I failed Don't Tread on the Bear by being with Caesar's Legion.

I honestly expected that she would storm out and leave me, but she still behaves like she always has been (saying things like "Woah, why are you leaning in all of a sudden?"). Why is that? I harmed the NCR and I bring her to the Fort and she still says the same things.

I guess I should be happy that Cass is still with me but she dislikes the Legion and she doesn't even say anything about my actions. Is this an oversight or is Cass just really indifferent about the NCR and Legion despite what she told me?

I think If you try to speak with her, shes leave you.

Cass is not faction dependent, but Karma Dependent. If you have very good Karma, the nukes won't turn you very evil.