Might get hate for this

I'm not hating on you for your opinion. But imagine being on her shoes. Her father died due to their blood. She was only thinking about getting justice for her father. I think if I were her the same thought would cross my mind too. Innocent people died because of their blood. She wasn't thinking about them at at that moment but then she thought of celphi and she came back to her senses. The character seems original that way.

That's still fucked up in a way, they did not know their blood was being sold. They even checked with distant relatives daily to make sure their secret wasn't revealed before finding out. They aren't at fault it's the person who was selling the blood and her stepmother for killing her father. The only reason why she came back to her senses was Celphi, so yes she does care about him. What about everyone else though?? What about her husband, his grandmother, his cousins, his sister. What happened to literally everyone else in his family??

Her stepmother, her stepsister, her past lover and the person selling the blood are more than enough for justice. Everyone in their family was innocent, so like I said they didn't ask to be born like that. So that thought of throwing innocent people under the bus claiming they need to take "responsibility" is more than enough reason for me to not like her. Because those people welcomed her into their home, they showed affection for her, they believed her story of traveling back in time even though that's crazy as hell and no normal person would believe that. Also they were extremely apologetic once they found out about their blood being sold. It just doesn't sit right with me, especially since she was once in their shoes. Believing in and loving a family member who had malicious motives.

Please reread the manhwa since I guess you've a misconception towards the MC.
First and foremost, the MC didn't know about what "substance" killed her and only approached the ML in the hopes of her and her deceased parent's inheritance will be safe and that she can get her revenge against her stepfamily and soon-to-be ex-boyfriend. Until she dies a second time that she finally knew about the "blood", which will soon lead to a series of horrifying facts regarding the Lapileon curse, her and her father's deaths, and of the source of this "cursed blood".
Imagine knowing these things for a brief period of time. Imagine knowing that the person (or nobility) you want to rely on to get revenge against those perpetrators would also be linked (though unintentional) to your death. As long as I can remember, she didn't get a breather all through this. Yet, still got on track to what her main objective is.
And for the record, Pereshati never claimed that they should take responsibility towards their deaths due to their blood. It was the family, especially the Previous Grand Duchess, who felt they should take responsibility towards the incidents (not just the MC and her father's death but also those allegedly died due to their cursed blood) and felt guilty towards the MC. Thought acted coldly towards the Lapileons after knowing the truth, she only harbored resentment for a brief period of time and would come to the realization that her anger towards all of this should not be directed to the Lapileons, but to the people who betrayed her trust and was set on killing her (which is the stepfamily and the ex-boyfriend). With this, she will settle her personal affairs and after being given a break, would strengthen her relationship towards the Lapileons and so on.
So, I don't really get what your saying is and you might have miscomprehended the manhwa (either misread the plot / might have jumbled the sequence of events / had a hard time understanding what was actually said and pointed out in the manhwa).

I forgot what I said so let me reread what I wrote

I can see where you are coming from, but from what I remember she did say they should take responsibility for the people who have been murdered. She even went on to think that even if it damages their reputation it was none of her concern. But I don't know maybe I'm wrong about this whole thing, considering how many people disagree

their reputation is none of her concern tho in that chapter, if the possibility of their blood getting leaked out and having innocent people getting killed like his father its normal to be suspicious around them

It's just iffy to me. Like I said, they welcomed her into their home and showed affection for her. Then she comes to the conclusion that what happens to them is none of her concern?? Yeah okay..

Being welcomed is not a reason to not doubt them, their blood is literally being sold and innocent people have died, for me what she feels is totally normal.

Your not making any sense. The Lapileons only "welcomed" her into the family after Pereshati brought significant contribution to the family by initiating and helping them solve the truth about the "curse", which is big deal to them since a lot of innocent lives are involved (the dead ones, the "returners" like Pereshati, and Islette). They also only shown "affection" to her after all of MC's perseverance in creating good and harmonious relationship with the Lapileons. It is actually Pereshati who "welcomed" and showed "affection" to them in the first place since the Lapileons are known of being reserved due to the "curse".

I'm not supposed to hate you, but what I can say is that your mind is shallower than a bottomless pit. Don't jumbe out the events that happened. It is not how they did it, but who acted first. The Lapileons only responded to what have Pereshati done to them. They were in doubt of her, so she worked hard to earn their respect. To be acknowledged of the title the Grand Duke gave to him. From the passing of time, it is only normal that they show gradual affection to her. It is also natural of her to whiplash on them. She and her father and a lot of people died due to their blood, for Christ's sake. They might not be the ones who did it, but it still their responsibility as the ducal and prominent household of the society. But the question is did Pereshati lashed out to the family? Like what she would supposed to act after knowing the truth? Nope, she did not. Her grudge doesn't even weigh more than her contribution in solving the case and her affairs. And yet, here you are, being ignorant of those facts. Claiming Pereshati is of vile nature after the Lapileons "welcomed" her. When in fact, she was the ones who saved the Lapileons from a darker route.

It is either you don't read the texts, you don't know how to read and comprehend texts, or you haven't read the manhwa at all.

Another thing, what do you even mean by "is welcomed and shown affection for"? Remember that they are in a contractual marriage. The only event which she was truly "welcomed" as a part of the family was in chapter 104(?) after being properly introduced in a noble event. How could you even imply that Pereshati should not "act like that" towards the Lapileons without missing the first 100 chapters.

well said like seriously Her father was literally killed and so as the other innocent people due to their blood yet their disliking pereshati being doubtful towards them?