Ok, wait for someone to love your significant other and try to kill you out of pettiness and see if your thinking changed somehow. I can see you wanting to be with the man you loved, but just because you love someone doesn't mean you should go around killing people. Her punishment wasn't really that bad either, she's still going to live and live with nice people and food to eat.
Everyone wants the person they love to love them back, that doesn’t mean you commit attempted murder :O
Wanting the person that you love to return that love is completely normal. What's not normal is trying to kill the person that your love is in love with b/c you're jealous...TWICE. Rose pushed her in the water and left her to drown. Luckily, Zeronis saw FL fall in and went after her. Then, Rose kidnaps her and tries to kill her by starving. How are these things NOT that bad?? After all of that, she didn't get put in jail, or put to death. Rose got sent away to live as a nun. She got off waaaay easy in my opinion.
lol I din't even finish reading all this, but I said it was MY OPINION fine of your not ok with it but there were more extreme things I have read people do. I once read a manga a girl said something along the lines of people going into managas and fall in love with the main characters and make friends with the other, and everything turns out but what you don't realize is you just destroyed a couple the "original author" would have wanted and all for their selfishness.
There's a whole ass few chapters prior that dealt with Ripley's conflicting feelings regarding the ML and how she felt guilty for ruining the original plot... Did you finish reading those chapters? Besides in this case the original FL doesn't even like the duke. Also Rose never got the chance to be with the duke even in the original plot, so it's okay for Ripley(the transmigrator) to take the ML when the FL doesn't want him.
No offence but Rose did bad, I know she really messed up but if you see any maga like this they always do extreme things so I guess she isnt the most horrible person, the FL turned like the basing FL, justice for Rose all she wanted was the man she loved to love her if you were in her place you would probably want that too. THIS IS MY OPINION.