Changing the story is the whole point of any work with a premise of a character entering an already existing one. Otherwise what's even the point? Just tell the original as it was. The example you've given is also pretty counterpoductive - while at one point in the story it is theorized that Olivia was robbed of opportunities for growth by the MC looking out for her, it turns out to be false. Thanks to that she was able to focus on developing her passion for magic and ended up much more powerful than expected. Her breakdown stemed from being made to doubt the intentions of her only friends, which could indeed be seen as suspect, as she was a commoner and the nobility of that kingdom were known to treat those horribly.changing history in a series like this can be dangerous. Take the manga, the world of otome games is tough for mobs. Mc of that series repeatedly saves the game s heroine from tragedy which she should’ve overcome by working with the male leads, slowly building up her confidence. Instead, she feels like a burden and is constantly depressed and criticizing herself for the first few arcs. Stories are designed to happen for a reason and removing a single element can mess everything up