Maybe rude is a better word then? Especially to Kirk.
Let's see where Uhura is 'rude' to Kirk:
- she gets into a bar and a drunk dude hits on her. I guess her not being interested and her being annoyed by the unwanted attention is rude. She's beautiful, she must expect that to happen, right?
- she gets into her room and starts undressing because that's is her room..only to find the same dude hiding under her roommate's bed, essentially spying on her while undressing. How rude for her to tell him to get out.
- she is partecipating to an academy test but the dude playing 'captain' is using the test as some joke and doesn't take it seriously compromising the simulation, and ultimately he cheats. How rude for her to be annoyed or sarcastic like dude's best friend also is. After all, all these cadets had time to waste for Kirk's little show and maybe the whole thing would badly affect their academy curriculum or it was their only, or one of the few, chance to partecipate to that test and show their skills but who cares. You don't think the simulation had an important purpose for them.
- the same dude is constantly insubordinate with the acting captain of the ship where she works and in a time of crisis where they are all in danger, that person had just taken advantage of the acting captain's grief for the loss of his home planet and mother to become the captain in his place . A cadet without experience who had cheated on an academy test and wouldn't be on the enterprise if his friend hadn't sneaked him aboard, a cadet that for all Uhura knows is just trying to get a personal revenge against Spock all the while earth is in danger. How rude for her to say she hopes he knows what he is doing. After all, his friend is also super supportive.
Not even taking into consideration how she must have felt watching Kirk tell the man she loves, and who she knows is suffering, that he doesn't care about the death of his mother he had literally watched die that same day. Do you also have any idea how humiliating it was for Spock to lose control like that and attack Kirk? Man, were his actions bad but why you think no one stopped him (but Sarek) and defended Kirk? (Not even his friend!)
Tos Uhura was 'softer' and she would be nicer with Kirk, sure.
And again, how is that Uhura is mean or rude yet, Mccoy's own behavior with Kirk (and Spock) is not?
Kirk had to earn Uhura's respect , and he did eventually. She represented the audience that might be sceptic about him being a good captain. Both her annoyance and then friendship for him in the second movie make sense in context. Their dynamic is sort of like the kirk/spock one, I might even say it's actually more realistic and consistent in writing than theirs. Neverthless, she isn't more rude or mean than Kirk and Spock (and Mccoy) are.