i don't really think so, I might be wrong -- but i think its intentional for them ( author-nim/artists) to include that. I think they're trying to make us think that she's evil although she's not ( like a plot-twist or something ). Seeing how they put this menacing aura around irene only to show that she didn't mean harm makes me think that the author was probably teasing us.
Reading these past few chapters makes me think of irene as someone whose genuine and only wanted to get along with her sister. Once again, I might be wrong, as i am only stating my opinion.
I'm going to look back on this and probably take this back if it ends up in a plot twist but: (tad spoilers if you haven't read to recent chapters)
I think her sister really does care about her, you can see her inner thoughts when she's nice to her - but I think she is upset when her sister doesn't open up/trust them with information like the academy thing and also when the prince took her away the chapter after was concern for the sister more than anger for it. Almost... an over protectiveness/bratty behavior which stems from not being close with her sister?
She's a siscon everyone
I think the sister is hiding something. I wouldn't call her evil just yet because she did defend Sylvia not knowing Sylvia was there. And she admitted that she didn't like the crown prince for being close to sylvia.
But it's weird because these past chapters have been showing Irene with like a shadow around her face and that usually means something weird is with the character