To be honest, it's not really Brianna's fault she looks like that. You can make the argument that she'd be better off dressing better (I agree), but I can explain a few of her fashion quirks in ways that don't make her seem pants and are perfectly reasonable. I'm doing this solely for the sake of clarity. I've criticized Wu like crazy, so don't think I'm going easy here.
For one, the "stains" on her leggings.
Take a closer look and you'll see that they're not stains, they're mostly
dust marks. These happen because she constantly crosses her legs. She wears boots and those attract dust like crazy, especially ones with those kind of soles. Note I said mostly. There's a few there which I haven't been able to identify and Wu isn't exactly known for clean living.
The dandruff is undeniably a side-effect of her hormone shifts worsening an existing problem. This is actually worth discussing but there's really no cure for it and thousands of people have some version of this (though not as bad).
The problems with her hair condition is due to constantly coloring it. Her natural color is most-assuredly
not reddish-brown and blood red.
Her hair issues boil down to the fact that she has a forehead reduction. For more info on this, check
this article on Lolcow Wiki.