Short answer: Designed objects that are not based on IRL objects will *always* fail somewhere in the cosplay construction phase, be they props OR costumes, and the solution is to simply: simplify. Fearne's staff is a series of very pretty arcs and lines, but since it is not based on a simple IRL object like a stick, its weight and balance get really tricky. There are ways to combat this with some careful material choices and some serious design simplification.
Long answer: Since the staff bends away from a load-bearing structure (like a straight line), has the same visual weight all the way down, is TALLER than the wielder, and has a lot of weight at the top, the whole design is destined to fail in a lot of places. MANY cosplayers way smarter than me have already simplified it into a working IRL object that solves its weight and balance issues, but here's my take on why it's failing.
I want to point out first off that there are lots of things about costume design that are not taught in normal art courses, nor in vis dev, and many things that are taught in costume design do not translate to costume CONSTRUCTION and vice versa. No one is an enemy here, nor am I advocating for a Fearne staff overhaul in the design stage (hi agarthan, BIG RESPECT), I just like doing breakdowns and I make a lot of things in and out of theatrical costuming and cosplay, so let's break it down where an "accuracy or bust" approach may be hindering the practical magic.
There is definitely a good and genuine "I want to see people succeed in their pursuit for accuracy" angle here, and I want to honor and fully celebrate that. In some cases with large companies, like PlayStation's "Aloy cosplay guide" page linked here, suggestions and designs are well-meaning but not really practical. Why would Aloy from HZW wear velvet in the technofuture? Is velvet next to the skin practical for an area that sweats as lot, like your neck? Does this material actually look and drape like velvet? (the answer to all these questions are: no.)
That said, I love this sort of guide, and I'm glad to see CR artists continuing in the tradition of putting out explainers to help cosplayers out.
Back to Fearne's staff. The design itself? Breathtaking, but not based in a physical use case (it didn't really *need* to be designed that way, but if we're making it physical, we gotta get picky here). In the grand tradition of many high fantasy designs, we're departing from reality in a way that makes it difficult to construct in an "accurate" or semi-accurate way:
As I illustrate in the sketch above, the weight of each piece follows gravity downwards, and the staff's top is pointing out in all directions. The first 1/3 of the staff seems to have no central structure or cantilever for each bend, so we're in tricky territory already- a branch like this IRL would balance itself with leaves, small twigs, or be supported by a thick central trunk, but neither exist in its now-dead state. There are also thin areas in the top of the staff that would fail to support these bends. To my eyes, I would try to find a central structure to build off first, like a piece of PVC pipe. Weight issues can usually be solved by making the material LIGHTER than the central structure.
To solve this weight and strucutre issues, it's smart to start with a normal and lightweight cosplay material like foam, PVC piping or 3D printed plastic. But, then we're in hot water- you attach PVC pipes together with connectors and 3D prints and foam with glue. PVC connectors are usually heavier than the pipe itself, which makes adding all those bends in the top half very tricky, since they are supporting themselves against MORE bends and no central pipe. Foam could be used, but would not stand up on its own very well, and would end up needing a central structure somewhere before it shakes off your flowers like dead leaves. Gluing 3D prints together with 2-part epoxy creates brittle failure points and adds weight, so we're looking at at least a handful of heavy attachments. At this point, we are gluing connectors to connectors and angles to angles, with no central supporting force, which makes it a HUGE challenge to balance without tipping over or breaking.
Adding hot glue, texture elements like foam or thermoplastic, flowers, and then the lantern to the top adds MORE weight, which means a cosplayer making this would be essentially carrying around more than 3/4 of the weight in the top 1/3 of the staff. PVC or ABS (printed) plastic are simply not strong enough to carry that much weight and distribute it downwards with that many bends and failure points, hence the snappage. Constructing this out of steel or other metal would solve this, but that's not really an accessible cosplay material, so that's out.
Then, about halfway down the staff we have one big critical bend- essentially one big stress point, where you'd have to add glue or a big weighty PVC connector or both. Bad news. The rest of the staff goes on in the same thickness as the top half, which fails to support the weight of the top or direct the gravity of said weight downwards, ending the whole thing in a wobbly, weightless flange that makes it difficult to carry. If you've ever cosplayed a character with a staff, you may know exactly what I mean- you've worked so hard and added so much detail on the top half that you end up with a wet noodle of a staff that neither supports your weight nor supports itself. In the end, you're carrying around an upside-down broom that makes your arms hurt.
But wait, not all is lost! The solution for me is to simplify the staff down, and consider weight, length, and distribution.
A great example of an ultra-simple top-heavy staff design that I think solves these issues is Marceille from dunmeshi:
There we go, an obvious connection point, weight distribution, and a short staff that's easier to carry without bonking it against stuff until it breaks.
The suggestions here can absolutely be applied to Fearne's staff without totally redesigning it, and many cosplayers have already simplified it enough to make it work. TinkeringPixie's Fearne staff has dramatic bends that make the staff a real showstopper, even while simplifying the bends and lengthening their arcs for support, i believe using PVC pipe:
Seirin Cosplay's Fearne staff utilizes a strong central structure to evoke the same design of the OG without creating many failure points:
And there are tons of other examples and ways to approach this staff without losing the overall design language of the thing.
Since we're creating something based on a FANTASY object, and it's ultimately up to cosplayers who are passionate about these characters to really sit down and problem-solve even totally unreal designs. If it's fun for you to make something accurate, have at it. It's my personal goal to throw away accuracy in many cases and warp them so that they work for me, but both approaches absolutely work. Starting with simple shapes and IRL garments is always, always easier for me than starting with a design and trying to troubleshoot.
I always appreciate it when designers break down their work, but more often than not, actually constructing an object will reveal its limitations, and trying to reverse engineer a fantasy object is more of a headache than it is a help. Start with something real and time-tested, then add rather than subtract, and the difference in your costume will definitely show through.