Give her broad shoulders. Give her a tgirl slouch. Give her a dejected anxiousness that's covered up with a faked brash devil-may-care attitude. "Oh yeah I just threw this shit together, it's not like, anything special" for an outfit she's calculated will strike the balance between effort, dishevelment (to lower other's guards) and still getting read as a girl. Give her all the character of her own doomsday devices, of her own dice: wild unpredictability masquerading as a calculated result that was always intended to be like that. This is the essence that must permeate your Vriskae, and it starts in her shoulders.
At all times she is vulnerable and at all times she is aware of her vulnerability and her biggest goal in life is making sure you do not find out. Nevertheless, she betrays herself. You can always spot it if you know what to look for. This starts in her shoulders as well. She hates them.
At the same time, a Vriska would not be a Vriska if her shoulders were not broad. She hates them but they contain her essence. She would not be all this if it weren't for her recklessness, if it weren't for the ways she compensates, overcompensates, drowns you in the deluge that makes you forget to even look at her shoulders. You will be dazzled by this Vriska.
So she does not attempt to hide them. She would never forget what - or who - made her who she is. She wears her shoulders... well, not on her sleeves, but in them. Comfortably snug inside a jacket that fits them, without any A-lines present to try shape a silhouette. She is who she is, she (faux) confidently states.
Shoulders confidently on display, a Vriska tries to blind you (to them). She slouches when you're not looking, but if you're there for the show, her energy leaves that slouch behind. Don't trip over your own feet trying to follow her.
I am once again shouting as loud as I can that everyone needs to read godfeels, or: "i dreamed of feeling better". It has so much more than broad-shouldered Vriska....