Hey brainstewd! and WELCOME to the forum!
Great questions and fabulous hairstyle from Eva.
Updos like this are best done and hold up better on hair that is NOT freshly shampooed. You will want to shampoo it no sooner than the night before. Please make sure you have put product like gel or mousse on your ends to help hold the style in the next night. And I strongly suggest you enlist the help of a trusted friend for the back where it's difficult to work on your own head.
I would definitely start with a ponytail for this, not pulling your hair back too tight of course, basing it about an inch or so down from the top of the crown of your skull. You may want to "muddy up" your roots to help dirty this area a bit. Too silky hair will have that band falling out and ruining all your work and the look. For a dance, you will want this strong foundation for your hairstyle so anchoring this ponytail is essential. Make sure the band is tight, not the hair pulled back into it, just the band itself. Make sense?
Leave out (to style later)
a front section from the part over to the opposite ear (how much is up to you : ) and a little at the nape of the neck to pick up some messy strands to continue from where the ponytail pieces will leave off that will go down the back of your head, to and past the neck. Maybe experiment with this a bit before the night of the dance. You
may want to part off a small rectangular or triangular (depending on your hair's density and head shape) section at the base of your skull for this.
Wrap a tiny section of hair around the band first to hide it. Next, you will need some anchoring pieces around the ponytail. Small sections from the very outside of your ponytail, loosely pinned down all around the base for symmetry and guidance. These help your sections have something to adhere to and they lay a base out for you to start your artwork. Leaving the main bulk of your ponytail in the center, picture the outside tiny sections as an octopus' tentacles (though you don't need it to be eight of them, maybe about 5) all around
leaving the center front out of this. Using hairpins (the ones that look like a tall "u" shape. Trick with anchoring these to stay is to squeeze them together so that they overlap like an X shape, insert them slightly, twist flipping them over and insert firmly towards the center of the ponytail. Takes practice...watch your scalp...ouch!
Continue to take small sections off this center bulk section of the ponytail. Decide if you need to apply some mud or clay to the roots of these sections too. You'll know, cause you know how your fine hair can be and if it might need it. Backbrush EACH section as you work, a little bit near the scalp to separate them from the all the rest of the style while working and placing. Place as you wish, putting a little "bend" in half way up the length with the size curling iron you choose. No need to worry about balance or perfection too much as this IS a messy look.
Some gals' hair won't curl easily so they need a smaller barrel iron for it to still have some bend when they are finished. Some curls too easy, so they need a big barrel curling iron. Do NOT comb out these bends. Spritz them with hairspray near the scalp as you place them here and there. You may have to stop every couple of sections and concentrate a hair dryer on LOW setting (so as to not blow the all deal off your head) onto the scalp area where you sprayed with the hairspray to let that section know you mean for it to dry and stay right there!!! The stylist appears to have worked with fair sized sections of Eva's hair since she has such density. If you do too, then adjust sections accordingly. Practice to learn how many sections it will take to fill in from crown to nape with an overall sized shape you like and yet still have the bedhead look.
Continue doing this as haphazardly and messy as you like making sure the back strands are connecting nicely to the nape of your neck strands, placing "bends" in them as well. Remember ONLY spray with hairspray at the scalp end of the strands as you are working. You don't want a stiff "do".
Bend the ends back away from your face on that front section. (sounds like you have some framing to work with at just the right length). Make sure you don't make this section too curled or else it will be too short and too uniform.
Okay now check the style out from all angles, adjusting areas that need "filling in", etc. Once you like the overall style, spray lightly all over now with finishing spray. A nice touch is to take a teeny bit of hair wax on the ends of some of the tendrils sticking off, here and there.
Good luck!!! Post us a picture from the night of the dance. We'd love to see it!!!!!!!!!!