spoiler:
yeah the dad pretty much knew the whole time in her first life but he wanted to be "fair" that's why he kicked out the first wife because she couldn't have children ( but she was actually pregnant when she was kicked out, fl mother is the second wife ) but before the first wife died she made a deal with a devil to take revenge on her family so that demon possed cossette body( real cossette is apparently dead). And the reason why fl couldn't do magic was that every time she tried to do it her magic energy (whatever you call it) and suck away by cossette that's why it seems like she can't do it when in reality she can. After Fl died the world pretty much went into ruin and the father wanted to fix it that's why he rewind time. Im not completely sure tho why the fl got her memories back I think its because she was the "Good one"
I’m always curious about what happens when after she died in her first life like did her father realise that CosetteTheBitch was a fake and did everyone suffer??...cause I hope they did.