Man, there is that once continuity error that bugs me.
The Decorations Error.
It's either someone setting them up to keep the school party going, Marco set them up hours later for another party (Star's possible return), or the crew really screwed it up with no logical expression giving a care in the world about continuity.
Like in Diaz Family Vacation when Star, Rafael, and Angie jump. You can see when Rafael starts to hug and jump with them, Angie's shirt appears smaller/changes shape while Angie's hair is now knee length like Star's.
And in Heinous, when Angie sits down, you can see when her body tilts down, her hair partially disappears and and it looks longer.
Also in Return to Mewni, when Angie kneels down with the laser puppy, her body appears smaller than usual, causing her to appear to have longer knee length hair. When she stands upright again, her body size and hair length are back to normal.
So I'm think if she straightened her hair, it will be floor length
Ok...this is quite an odd thing to fixate on yet I understand what you're saying. Movement can be hard to animate and it leads to errors. I'd say that it's curly and that would be the end of it. It may look poofy, but so does Moon's and Star's so it's hard to pinpoint.
I agree with looks poofy and with animation errors, her hair changes shape and volume sometime. So, in final thoughts, it looks mostly wavy in my opinion but with curly ends all tied in a ponytail.
And I couldn't tell how her hair was styled in Hungry Larry, and if you know please do so. I think it was loose and wavy because you can see part of her hair upfront of her face covering her ears.
Not all of her hair is seen much like Queen Moon's while wearing a cloak in "Moon the Undaunted" and "Face the Music" but that's an animation choice. Hair is magic, much like Star's when it's all in a floral cap in "Royal Pain."