After a night of sleeping on it--and a conversation with someone who knows a thing or two about narrative structure--I decided I still might not have the Main Character Throughline down as well as I thought I did.
Essentially, I was keeping her struggle cerebral when really it should have been more external. With her Domain in Activity that should have been obvious, but for some reason her Concern of Understanding threw me off. I need to focus on things she does that cause problems for her, not the internal struggle to comprehend.
This is going to take some time to reengineer. But I think it opens up many new possibilities.