Turning a blind eye to one’s suffering is just as bad. That girl never bothered to help mc which is the same as accepting what’s happening to her. In fact all those times mc suffered for her she thought that was a normal thing. She’s spoiled to the core so annoying isn’t the only thing, she’s just as rotten as mc’s family.
Except that she'd purposely be dramatic and set up scenarios where her sister would take the fall and the punishment for HER mistakes (necklace thing). She'd make Hilise get punished for things she didn't even do sorta thing (sending her brother to harass her because she "attacked" her). So it's one of those "villainess who acts cute so everyone trusts her immediately when she accuses the good-natured and innocent mc" situations. She's perhaps mildly redeemable but at the core she's a sadistic manipulative cunt who will do anything to maintain her position
If you remember at the beginning even, the MC was in jail and to be executed in the place of her sister. I'd cast severe doubt on the idea that that was just her brother's doing, as Hilise expressed how often she took the blame for her sister's wrongdoings, and we saw her sister HERSELF set up the necklace situation to get Hilise harassed and put down. Her sister was likely most of the reason Hilise was in jail - she probably specifically manipulated others to make herself seem perfectly blameless and angelic and pitiable so that she could finally get rid of her sister and remove her from the equation

That blonde brat never shuts up and is a annoying as hell, but if you think about it, all she is is spoilt. She isn't that bad compared to everyone else, she is annoying and that's it. As far as I remember, all she did was crave for attention so she would make FL feel bad, but she never directly hurt FL or wish for her death like others, so I lowkey hope she stops beingg an annoying bitch and redeems herself someday