In context, my novel begins when the MC is extremely young, as in her birth was included in the chapters - that young. She is also the only daughter of a king, which means she is a princess to begin with, so she is already privileged. She also holds the title of Hope of the Kingdom, so people look up to her more. Also, mentally, she is a grown woman (because she remembers her previous life) - this is just extra information.
So, with all of her riches and powers, as well as being treated as someone above others, she is spoiled not only by her parents. Because she is also royalty, everyone around her is a "yes man." Realistically, if a person of sound mind (mature thinking) is treated in a certain way for an extended period of time, they will be affected and have a high chance of "adopting" to that kind of treatment. In short, she - a mentally mature adult woman - accepted what was happening and gradually developed the mindset that she is indeed "above all else."
Many readers are irritated by her, and I, as an author, am equally annoyed. However, this is necessary for the character to show growth and development rather than remaining a character with no flaws or stuff. Keep in mind that this is the MC, so it's difficult for me as the author to create such "unwanted character personality" for my MC.
My point here is that "flawed" characters are required for a story to be more than just a "story." Flaws, whether intentional or unintentional, bring the characters to life and make them more realistic. No author would want to write a story with no dynamics or anything like that. What's wrong is when an annoying character doesn't grow and doesn't break out of her annoyingness - even without having their own arc.
I am not saying that it's good to be a (oof) as long as you have that "privileged kid" card, though.
My advice, create something about her that will make the audience like her. Tweak her personality or something. Or maybe, show the audience how she supports the couple, something like that, even if it's only subtle
