S01E03 of anime adaptation of the LN/manga The Devil Is a Part-Timer!
See here 1:18 - 1:32 There are these 2 characters Chiho and Emi who meet for the 1st time when Emi interrupts Chiho's profession (confession?) of romantic feelings to Maou, who is Chiho's seniour colleague and the title character. Chiho assumes Emi is Maou's ex-romantic partner. In the part translated as 'It's none of your business now!' Chiho seems to address Emi as onee-san.
Is that in like a sarcastic way or something? I thought Chiho would say something like 'omae' ? Or maybe it's a slight in pointing out how much older Emi is?
Actually, I notice the English dub has a non-corresponding part (see here 1:14 - 1:19) where Chiho says 'If anybody here needs to stop yakking, it's you, sister!' So is the meaning of 'onee-san' by original Chiho similar to the meaning of 'sister' by dub Chiho?
Note 1: In the English dub, 'sister' is not directly translated from onee-san because in the original Chiho is asking Emi 'Are you trying to say you're more intimate with Maou-san?' The 'sister' is actually 12 seconds (1:14 dub which is 1:40 original vs 1:28 original) after the use of 'onee-san' in the original.
Note 2: I think the dub is changing the dialogue vastly like trying to make it more of a romantic fight when in the original they're trying to understand what the other is saying.