She's super smart and can be an absolute sweetheart but she tends to scream bloody murder when she doesn't get her way, stomps her feet at me, and terrorizes her siblings(7 and 5) to the point of tears some days.

You did a good job. She's smart and sweet. She expresses her anger, help her find an outlet for it. Guess what? This behavior will only get worse. You need to find the why she is acting this way.

We've been working on it for a long time and are consistent with punishment and positive reinforcement.

Insanity: doing the same thing over and over again and expecting different results.

She's very articulate and capable of expressing herself with words

That's a good thing

, she's just kind of a (huge) jerk at this age.

So are you. How old are you again?

she's improved some but still has plenty of rough days.

She's improved is a full sentence. We all have rough days, no need to punish her.

Today has been rough and she's been fighting me on everything. I reminded her that Santa gives bad kids coal and she's not being nice to me. Now, I do have some coal candies.

She's acting her age. She'll be sad.