Never trust anyone who’s jaw doesn’t move when they speak.
That’s what they call Long Island Lockjaw.
It is supposed to make you look of High Breeding.
Haley is trying to combine the polite, acceptable, stately version of the Southern accent (as opposed to the redneck accent that Hitlery! impersonates when addressing southerners) with the Long Island Lockjaw of the Northeast.
It’s supposed to make her sound intelligent and of a higher class than the rest of us, you know, so we all bow down to her and give her lots of power and prestige.