Then I went on to write the next 3 chapters, all introducing critical elements to the book and overall series.
And then chapter 13 decided to let me know I wasn't finished with it just yet. Having decided what this POV character would be occupied with I realized that I needed a catalyst for her decision to return to her own castle, leaving both sons behind, rather than her simply deciding to.
So, I tried to continue chapter 13, to add in the catalyst. And it just came out all wrong. I didn't like what I was writing one bit. Something was wrong. And then, after deciding to ignore it and have a beer, I realized the problem:
Chapter 13 needs to take place in the POV's own castle, not in her cousin's. So, now I can chop off the attempt to add the catalyst, which was failing miserably, and rework the important event in chapter 13. But, I now need to go back to the earlier chapter with this POV and add the catalyst there to prompt her to return home.
And then, hopefully, I can leave chapter 13 behind -- until the rewrite of the completed manuscript.