while I think it's for plot. I also think the brothers are approaching MC because she isn't being nasty. obviously they know she isn't their sister by any means. she was a spendthrift and had a horrible temperament - I've had arguments with a "wall" before. where it just rounded back to insubstantial evidence and crude insults, and by the end of it, I started talking on their level. people are unpleasant to be around of but because of circumstances, it winds down to ignoring them and immediately becoming defensive out of habit
I hate the brothers, with how much the author had built up how MC hates her circumstances. I hope to see their perspective of what she was like before.
I want to see Iklies~