In my opinion this one is more complex than that. From what we can gather, Calista resented the fact that she had to kill Harper (both being broken and traumatized) and regressed time. She could've stayed in the timeline as the rightfull empress, loved by her people, powerful and rich. But she choose to give everything to bring back time.
From the book Harper read early on, to bring back time one needed the Dragon Jewel (dunno the name) and the right condition of despair/desire, you could have both and still be unable to go back in time, it was tricky and difficult, but Calista found a way. This also explain why she feels a sense of linger whenever she's with Harper.
Exactly what I was thinking. Time wouldn't have regressed if Calista didn't put in the effort to turn back time, regardless of whether she remembers or not. And she clearly carried some of those feelings back into her 2nd lifetime too, which we saw earlier on when she first appeared after the regression
Those stories where the trash father neglects or abuses the mc, then suddenly dotes on them in the 2nd life after they realize the mc is cute. So like, if mc wasn't cute, her sister would probably just kill her again tbh.