Yes she should be able to appear in chapter 11, but the code is so complicated I can’t give you a straightforward walkthrough. 😅 Try to keep Ning and Yao at the capital, then recruit them when you can, then they should usually be around where the Princess is. If you believe you have done those things but still ended up losing track of N, email me your save file and I’ll take a look if there could be a coding error.
But if it’s too much work don’t worry about it, it’s all optional narrative for flavor.
Also, thank you for your review comments! :)