Here's my dilemma: How do I take a strong main character who already fulfilled a transforming growth arc in the first book and repeat it in the sequel? Karlinah can only learn so many lessons now that she is part of "a highly favored people of the Lord" who "never did fall away". I found my answer in Jordan McCollum's Character Arcs. Not all characters have growth arcs. Some have a negative arc (where the good turn bad) and some are flat. The book explores these along with the traditional growth arc.
On page 61 Jordan says,"Sometimes the story is not a journey to improvement, but a proving ground of something the character has already learned." Think of the many fairy-tale characters like Snow White and Cinderella, where the good keep choosing to be good despite the hardships thrown at them. This is the Flat Character Arc. It can end happily ever after or in tragedy (though the character does not waver).
In the sequel I am writing, Karlinah's starting point defines her as already good. Her struggle will be that she is continually tempted to stay good. Think of the character pressing on against a headwind rather than climbing a mountain. It's simply a different kind of movement or growth. The temptations should grow worse and the consequences of those choices become greater. The character may not see rewards for making the right choice, making it more difficult to choose the right. There may be one final temptation to face in the climax, where giving in appears to have little consequence (but the opposite is true).
I am happy to learn that character arcs are not required to make a good story great. In this sequel, a flat character arc is what is right for my plot and character. There must still be conflict, but now my character has the freedom she needed to go in the proper direction.