The reason why the elite 4 hate Geeta the pajeeta,is because these "elite 4" are just summoned entities from the 3rd legendary ability (wich she has some sort of "pact" with for she wanted to harness this power), just like the manifesting of paradox pokemon.
Difference is,these are humans and not pokemon,thus they gradually gained consciousness and, once they realized it and pajeeta as well,she did threatened them to keep their mouth shut otherwise she would literally cancel their existence at any given time. Pajeeta has that alien look because she did partially took in her body a portion of this pokemon power; we will see her true appearance once the area zero dlc is completed and she will use the classic excuse "i was completely drugged from this power,i didn't do it on purpose" kind of bullshit. She will also use these imagined elite 4 as pawns to fight you again only this time having absurd over buffed pokemons ,kinda like the totems.
Last thing,after rescuing pajeeta from her drug addiction and freeing the elite 4 from her,you will be able to face off this wish granting legendary putting an end to it's evil scheme. I will shout about this as it's the true climax of the dlc explaining partially what terastalization is.