I'm a bit impressed - I guess I'm not the only one whose worldbuilding was influenced by real-life events. I tend to think a lot about that.

I had a fondness for adding random bandannas to characters long before the virus, and even considered a global pandemic as a possible reason for a species to outright abandon their planet if they were space-faring, but real-life events kinda makes it feel a bit insensitive to incorporate that sort of thing into fiction while it's actually going on.

In this girl's case though, I think she wears the bandanna in case there's a sandstorm. She doesn't like sand. It's coarse and rough and irritating, and it gets everywhere.

Plus, sand/dust is typically very hard to breathe...

Very true... I suppose one possible flaw of my way of designing "alien" creatures is that I play it way too safe with their designs--maybe I need to design some desert-dwelling critters that have evolved some natural defense against blowing sand, like some sort of glorious mustache or something.

I also realized I failed to give her any sort of protection for her eyes and ears, we can perhaps assume she has some goggles with her somewhere, but I'm not quite sure how to prevent sand from getting in her ears! Maybe I need to play with hats and headgear a bit, I'm sure a simple headband or hood would suffice, or perhaps she has earplugs with her as well.
Or, maybe nature has already provided her with a solution and her ear canals are protected by fur and hair?

As long as the inner ear is protected, the precise method isn't as important. So yes, that leaves a few options.
1: Perhaps if she's got some goggles, those have some earplug attachments?
2a: Or, maybe her people (or a people they have contact/trade with) developed earplugs that are harder to see (possibly hidden by ear fur)?
2b: Sub-option of 2a. Something I've done in my own works and mentioned to others over the decades. Back in the 90s, it was a more laughable idea. Nowadays, it's just a modification of something people can buy. A higher-tech version of in-ear hearing aid (similar to the earbud from the 2006 Knight Rider series), with a built-in feature to also muffle or block sounds (good for people using guns, working in high-noise areas but needing to communicate, etc) that are too loud/annoying. This is something close enough to the inner ear as to be invisible to most observers, unless you're really eyeball to ear with the individual.
3: Ear fur/ear hairs that form a lattice pattern by growing in alternating directions a ways into the ear. This would effectively create an "air filter" effect, but would still need one to clean their ears well after a sand/duststorm, to avoid any trapped sand/dust from trickling into the ear.

I recently watched a video on what forms alien life could take, and why. Your mention of their world as "Space Australia" actually hits on something. Here on earth, we have (I'm going with present-tense to avoid headaches, since while the species is effectively extinct, the topic is on their genetics and form) the Thylacine, which genetically is most closely related to the Tasmanian Devil, but evolved in such a way that it most closely physically resembled a canine. This is an excellent example of how convergent evolution fills similar ecological niches with similar solutions. Sure, the Thylacine is still a unique and wonderful creature, but its canine-like traits are a result from the need for something to fill the same role that the Wolf and other canids filled elsewhere. Fish have 2 eyes, squid and octopus have 2 eyes, birds have 2 eyes, reptiles have 2 eyes, mammals have 2 eyes. Sometimes a basic design is something that "just works" well for evolution. Also, barring a conscious decision by a species or large enough group within a species, certain mutations that would eventually give rise to other things (such as evolution of "normal" arms to wings) is generally something that can't be evolved once a species has evolved past the point where the individual steps of mutation could have been advantageous, because those mutation steps now have become detrimental, rather than helpful. Long story short: Alien species may look more akin to what we know, because similar conditions would result in similar evolutionary solutions. This may be different for sentient alien species, if they've reached a point where they've decided to do things like trade hands for wings many generations ago. Or species that have been (willingly or otherwise) genetically altered to invoke these types of mutation.

As far as inner ear protection goes, I'm leaning toward some sort of natural adaptation if her species comes from an environment where sand is an issue. I'm not sure just *how* big an issue blowing sand would be, but I get the feeling that just tucking her ears down, combined with whatever ear hair her kind has, is probably good enough if it's just an occasional thing--maybe a simple set of earplugs tucked in her pocket just in case could help too, and if she's actually expecting to run into sandstorms she can probably come up with some gear actually suited to those conditions. I have occasionally been tempted to play with designs for masks, helmets, hats, and the like, maybe this is an excuse to finally do so.

I describe their world as "Space Australia" because that seems to invoke the sort of aesthetics I have in mind for the planet, a more arid "savanna planet" of sorts with plenty of deserts, grasslands, badlands and the like, and some forested regions in the temperate and polar zones. They share their world with my sugar glider/possum-inspired sapient species, which is an arboreal species, although I'm not sure just how commonly the two races interact or the specifics of their interactions (it would be mostly peaceful and positive, and probably mostly for trade, but with a bunch of specifics about the planet's geography and the two races' cultures figured out I can't really go into specifics yet).

Worlds having two or more coexisting sapient species is something I've realized is fairly common in my own world-building, be that through natural development, introduction of alien races into an environment, or other factors or some combination of factors. All themes that I think about fairly often, but never really make it into my art or even descriptions or comments on said art for various reasons.

All this makes me realize I should probably come up with a to-do list for world-building, although I'm not sure how well a lot of things would translate to any format besides a text document.

Admittedly, a lot of my "alien" designs looking quite terrestrial is just a result of my janky creative process--if I'm bored and start doodling a creature, I might just decide to call it an "alien species" rather than trying to fit it into an already fairly established world. This means that a lot of what I call aliens reflect my aesthetic tastes. I suppose a similar comparison could be made to how most aliens in Star Trek are humanoid, it's easier to apply makeup to a human actor than to create complex puppets or costumes, and in making these aliens still look familiar to us they may actually serve their narrative purposes better as they're not distracting (for lack of a better term) in a way that would take the viewer out of the story.

Of course, from a more scientific standpoint, there is that element of "reinventing the wheel" when it comes to character/creature design, where trying to make something "look alien" might actually sacrifice practicality. I feel that way about a lot of alien technology in fiction, too, where something as basic as a gun gets a redesign to make it look more like a sex toy than a weapon for the sake of "looking alien" or the use of wheels is intentionally avoided despite wheels being a very basic application of physics.

The thing about being relatable for narrative is actually why the Engineers were "reengineered" to be basically human for the "prequel" Alien movies. It was figured that people wouldn't find space elephants as relatable... This also is why a planned answer to what the Things were doing aboard the alien ship in the The Thing prequel (and precisely why the ship crashed) was scrapped. The fear that a human audience won't relate to non-humanoid species is pervasive enough that shows like The Outer Limits have done episodes where it's the ugly, monster-looking species that are the goodguys and the "beautiful" humanoid species that are the evil planet-killers, but the humans instinctively side with the badguys.

But hey, not everyone can be an amorphous shapeshifter. Not even all of my fursonas...