I don't want to assume such a thing, it's my considered opinion from the available evidence. I don't subscribe to the idea that there's an awful lot of difference between someone who is wilfully ignorant (ie. an overt racist who for example uses racial epithets as part of an insult) and plain ignorance: someone who in this freaking day and age still hasn't bothered to examine their thoughts and feelings on topics like race, gender, sexuality, etc, and then proceeds to discriminate against people because of it. Anyone who has worked in a customer-facing role should have engaged in reflective practice every time a slightly less-than-stellar customer service situation has occurred, or when they find themselves thinking things about people and critically analyse those opinions. She was a freaking manager. How can she not have done this already? I've never been a manager and I do it all the freaking time!
Furthermore, trying to determine whether someone was acting due to unconscious bias or they're just trying to cover up their intended bigotry is an exercise in futility IMO, and even if I somehow knew for a fact that in this case it was implicit bias with regard to race as opposed to overt racism, it wouldn't change my opinion that it's time this person looked for another job and more importantly reflect on their intolerance; maybe she'll conclude that it's not her fault but society's and she was made a scapegoat by PC types in management bending over backwards to appease the Cult of the Extreme Left and maybe subsquently upgrade her status to a full-on racist. Maybe she'll be more careful in future and confine her racism to posting dick-ish things about non-whites on forums/social media under a different name. Maybe she'll own her actions at least to herself and consciously make the effort to ensure she won't do any stupid shit like that again. Who knows.
You've already made this argument, I've already responded to it. This isn't anything new.