The early novels where Jade appears definitely showcase the main cast right out of the gate. In 'The Reckoners' trilogy, which starts with 'Steelheart', she's introduced alongside David and the core team almost immediately in that first book. Brandon Sanderson doesn't waste time—you meet the key players, including the mysterious and sharp-edged girl who can turn things to crystal, right as the plot kicks off. It's a very efficient character rollout.
That said, I find her initial presentation a bit... functional? She's clearly a major player, but her deeper motivations and the complexities of her powers come into focus more gradually over the series. The first book establishes her as a powerful and aloof figure, but you don't get her full backstory until later installments. Some readers might prefer a slower, more mysterious intro, but this approach gets you into the action fast.
Honestly, if someone is picking up the series specifically for Jade, they won't be disappointed by a lack of screen time. She's there from the start, throwing attitude and crystalline spikes. It just takes a while to peel back all her layers, which I think is pretty standard for epic fantasy. You get the core persona upfront, and the nuance follows.