Yes, don't forget that she comes from modern Japan where, as a high school student, she is more dependant on her parents than these noble children are in terms of social interaction and etiquette. From what I've read in the novel, she's become completely dependant on the prince and his followers in place of her parents because she doesn't know any better and has no one to help her. She's only like 15 or 16 and not very mature. A sweet and booksmart girl but basically a child. The bullying she's experiencing is solely the fault of the prince and none of the girls at the academy realized until the MC spoke with Lady Ashley about her perspective.
Yeah. In the world she comes from friendships between different genders aren't taboo. Even if someone has a significant other. So long as no actual flirting is happening it isn't cheating.
Of course that prince is a real problem, I doubt based on how he behaved from the start that he hasn't been flirting with Aria.
I really hope they help air chan and that airchan is in reality just clueless and kind and teach those nobleman some lesson