Alda isn't a character. Alda is a mask worn by Aldamurisse. (Have I misspelled that?) So you can't show that in the ordinary way. Her 'development' turns out to be important to the Quest--the key to its success, at then end. And, at the end, Aldamurisse chooses to act when she could hide. Play that up.
From the beginning, your base story has Alda/M moving from choosing to hide to choosing to act. She cares about stopping Ghen (though we don't know who he is yet) (and she isn't sure of herself--uncertain depths in the character behind the mask--cue Angel of Music). Bit by bit, Mask Alda comes to act with more knowledge. Aldamurisse lets her knowledge out because she cares about Tazar. He's such a good soul, innocent not of knowledge but of ill-will, that she has to care about him. He's a puppy with the wisdom of a sheepdog and the power of a war-dog--and the humility always to listen and learn. Tremendous character--and your original intro, in the prison, was perfect..
By this time the reader knows that something is going on inside Alda. But we should discover it when mask-Alda comes to learn who she really is.
You can't show Alda's development from the inside, because the inside is Aldamurisse. And Aldamurisse is a secret to be hinted at, then glimpsed, and then finally revealed when only she can clear the field for Behira's forces to survive and win the battle.
I'll be trite: Think how Marvel Cinematic would handle Mask Alda/Aldamurisse. Not the smash, bash, and crash, but the reveal and the eucatatrophe. Jaylene: She has saved my life! I, the Lance of Behira, have vouched for her. Founder: You cannot vouch for what you do not know. This is the cowardly sister who betrayed Behira! There is your story, juices dripping from the red meat.
As far as the Catacombs and the rest, you and I both need to embrace de Saint-Exupéry's maxim: Perfection is achieved not when there is nothing left to add, but when there is nothing left to take away. (More on my forum.)
(de Saint-Exupéry's introduction to The Little Prince is one of the most beautiful paragraph's I know.
To Leon Werth
I ask children to forgive me for dedicating this book to a grown-up. I have a serious excuse: this grown-up is the best friend I have in the world. I have another excuse: this grown-up can understand everything, even books for children. I have a third excuse: he lives in France where he is hungry and cold. He needs to be comforted. If all these excuses are not enough then I want to dedicate this book to the child whom this grown-up once was. All grown-ups were children first. (But few of them remember it.) So I correct my dedication:
To Leon Werth,
When he was a little boy
)
