[...] but honestly I haven't gotten beyond a broad outline for the upcoming chapters, so I haven't gotten down to her specifically yet.
Honestly, that's something to fix
urgently. Of course, as a creator, it is often the case that you may have to slightly adapt and change plans in small ways as you go through the creation process, but you should always
have those plans, and that the plans should be like a fully detailed blueprint and not just a loose idea.
Building a good story experience is a bit like building a bridge that transports people from one place to another. You need to know in advance where the supports and pillars are so that each span of the bridge can align and hold the structure.
There's many good reasons that people talk about 'the narrative arc' when referring to either the story as a whole, or the story of any particular character. A narrative line is just too simple and straightforward. The artistry is all in the graceful arc that flows smoothly but doesn't allow the audience to immediately predict where it will go. But to engineer a perfect arc, every piece that goes into it has to be perfectly angled and aligned.
The builder has to know exactly how big the whole arc will be. You absolutely need pin-point accuracy, and making it up as you go along won't allow this. Instead pieces won't align properly without being padded or shaved at the last minute of fitting, creating scenes that feel out of place or poorly aligned. The arc will be a little ragged rather than smooth. Some parts will instantly be seen to be forced in.
You absolutely have to commit to a decision on every scene eventually, so not doing so in advance doesn't actually save any time. Instead, making it up as you go is slower, as you'll waste extra time all along the process in those last minute adjustments to force a piece into place, or having to remake a piece that didn't fit the span right. It also adds a lot more pressure on you, the creator, which isn't good for you or the project in terms of successful completion.
Give yourself the advantage of taking whatever time you need to design what you are building before you build it.