Beyond the steampunk reasoning and period set nature talked on, here are other details.
Her appearance at least in her younger days was based from a headshot piece of concept art left over from the 90's that has managed to survive to today. It showed a lady very much in design idea to Inspector Gadget but with bigger flaring hair ( white ) and a mole. This piece of concept art is also where the idea stems from she owns a black & white cat.
I translated the white hair into it being platinum blonde. Only one other piece of concept art exists from the lost series and that showed her as a red head. But by the time I saw that art, I had already drawn Jocelyn's concept art and felt fine with *most of it.
*Her original prosthetic lower arm was more complex in the first design and had a now completely scrapped idea to it. That she could treat it as a form of musical instrument in activating different gadgets.
When the story of Smoke, Steam and Mirrors was still being outlined, I was feeling more and more revolted by reading of current events in the news. By this point in outlining I had already decided on the time being 1895 which I am aware is a period credited to have had a lot of international migration of people moving to the United States. With the horrid way some migrants are treated entering the United States for real in modern times. I felt it was fitting to show a fictitious one succeeding and beating the odds. Add in at that point in time too, in real life some very awful events were happening to me. Because the other characters noted as leads to the series were both male. It felt good to write for once a strong female character in the spotlight.
Through out the series you rarely see senior characters and at that never ones standing out. I don't count Von Slickstein since he's a side character in my opinion. When having the timeline jump into the 1940's I wanted to show both Jocelyn and Patrick were still active & ready to handle things. Although only showing not much slow down to what they could handle. Unlike other characters, I wanted the two of them seem settled in their ways and grown a lot since their younger days with the past still influencing them.
Jocelyn is the only character I get to have in my opinion fun with her outfits. Sure Victorian dresses are outdated by miles to today's fashion but they sure are interesting in design. So yeah, all her outfits gained concept art with color guidelines. Knowing of course styles had changed by the 40's had me not only adapting her dress sense to the times but turning it conservative also for the fact she's now one of ACME's heads. She has to come across as more business-like than superheroine in a dress meant to be mildly influenced by Batman in appearance. ( The clearest nod to that is her belt seen in Smoke, Steam and Mirrors. )