Uh, if you read carefully, she hasn't fully come back to life, she just transmigrated to different parallel words with the ml's soul fragments to take revenge for 100 years, but, her means of revenge were too ruthless or cruel that it made the world unstable, making all of the parallel worlds that she'd been in the same. These parallel worlds are kind of connecting to the real world, so when she's about to be reborn again in her real world, she couldn't because those parallel worlds are slowly collapsing, affecting the souls in it that are somehow connected in the real word, including her grandfather and that's why she decided to heal the trauma's she has caused to stabilized it. Anyway, it sounds confusing at first, if you're not in quick transmigration series, but every world has their own center or medium, it's either the male or female protagonist or even both, and if one of them suddenly died due to unknown or outside factors with them still being the center of the world, i.e with protagonist halo or plot armor still activated, then it would make that world collapse, as most of the worlds solely exists for the protagonist/s. Unless, they somehow managed to transfer that halo or take it for their own use, either by taking their opportunities or luck in each plot or by making them fall in love to yourself. There are different rules in each world but as far as I've read, this is the most standard one.
Her coming back to life is pretty useless because she let the same man treat her like s*** . Are we supposed to think she's a badass new Flash putting a girl in a badass clothes or drawing her badass does not make her a badass she actually have to act like one to be one the only ever good Chines fl I have seen is the girl from cheating man must die the rest is just a bunch of I look like a badass but I'm not cuz I let a men treat me like s*** who I said I wasn't going to allowed to treat me like that （￣へ￣）