Responses
I'm freaking diabolical I would have the time of my life and enjoy that shit. Plus no one would be hurt cause they would never be a thing. But, I get what you're saying.
But in the previous life she did what you just said and got the girl with her brother, to use her. So now it's more about her thinking she doesn't deserve happiness and needs to repent for here past sins. Also, you can't force people to fall in love. She already changed so many things that it's not surprising that the story will take a different path.
imagine your favourite romance couple from a manhwa. Or your favourite bl couple. (For me, its haebom and taesung from cherry blossoms after winter.) anyway, imagine your fav couple. Then imagine getting isekai'd to that manhwa and then u mess up the original storyline and u make the other person fall inlove with you instead of the person in the original story.. u get in the way of the couple that you love/ship. Wouldn't that feel kinda sad and wrong??? (sorry if i explained that poorly. i hope u get my point)
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The situation isn't the same but the feeling is a bit similar...(thats what i think )