Yeah, but I think part of the ML and brother’s quick change stems from guilt. They knew her situation and did nothing, and only changed because she changed and pretty much became useful. They’ve had to acknowledge her change and the fact that they’re trash people just as bad as the ones they despise. So I guess it’s like a wake up call for them
I can’t argue with the other pacing issues you mentioned, but about the attitude switch ((SPOILER))
I read from another comment but apparently the ml and the brother have always loved her but never recognized those feelings because of how she acted, so in this life the fact she’s acting differently in a way that didn’t deter them away kind explains how they’re more willing to “accept” her... I guess. Also she ends up with ml in the end so there’s that.

this one is geniuenly hard to rate, because it does some things brilliantly and out of the box, while failing at simple stuff like pacing . The way she is aware how EVERYONE has failed her and forces them point-blank to acknowledge it? Wow, chills when she admitted she had died so casually. Also good for her for giving up on her fiance, I honestly hope she'll end up with someone else/no one - because as she poined out, he, as well as her brother, mother etc, just turned a blind eye to her being neglected and used. Rare for manhwa to admit it so loudly, without villainizing those people beyond return. The interactions with the ogMC/regressor are interesting, especially seeing it from that girl's perspective. What I have issue is pacing - some scenes feel short, sometimes info is randomly thrown at us in a way that feels forced, the changes in characters' behavior toward MC feel sudden (the ML and the brother especially, seriously, one interaction and you're already flipping 180??? that was all you needed????) and overall the quality is inconsistent. + the Imperial consort and the emperor are comicly cliché villains, hope that's not all we get. This manhwa is sometimes peak (especially the angsty moments), but sometimes so mid it's painful