This isn't wrong - Galadriel did go through her learning/maturing/"teenage" years - about 5000-2000 years before Rings of Power.
She studied under the Valar in Aman, saw the light of the two trees. She was incredibly proud and arrogant and stubborn and it did rub people off the wrong way. But she then exiled herself to middle earth and studied under Melian the Maia and that's when she matured, about 2500 years before the current timeline. By the time of Rings of Power, she was already the ruler of a nation. She basically decided to carve a kingdom out of Lindon (Gil-Galad's kingdom) and rule it and Gil-Galad didn't even blink and let her do what she wanted. Then she ruled Eriador before founding and ruling Eregion. You know that kingdom that Celembrimbor rules and the one that is under siege in the trailer? Yeah....that's Galadriels kingdom.
I understand changing things to be more "humanized" and so, but the change is so drastic it's not anything close to resembling the existing characters.
It's not just Galadriel's relationship with Gil-Galad that has issues, it's Elrond's too. Elrond was Commander in Chief of all Elven armies in the second age. The term "Herald" was expanded by Tolkien in other texts which describes in detail Elrond's relationship with Gil-Galad. Whilst Gil-Galad was technically "High King", most matters of diplomacy, war, administration was left to Elrond. He was basically running Lindon at this point. In Tolkien's own words, "When words were spoken from the mouth of Elrond, the kingdoms of Elves treated the words as if uttered by Gil-Galad himself," such was their relationship. "Sorry mate, Elf Lords Only" in season one was such a piss take to that relationship.
If they want to go through this approach, don't use the existing characters and just make the characters up because they are so different to what they actually are.