My opinion on Titania and her arc is that, while the concept is nice, the execution is very weak. She's brought up as a subversion of fairy tale tropes, but she doesn't do that effectively.
* Damsel in Distress: Titania does not subvert this. She's not a badass woman who pulls herself up by her bootstraps, especially not in EP15. Remember, before the player character went down the waterfall, Titania did nothing other than murdering grunts that got close to her. She wasn't even able to get out of the first room by herself. Then, later on, she pretty much goes all Leeroy Jenkins on the Meteor grunts and gets herself baited multiple times by Taka. She was entirely helpless during the whole thing.
* Knight in Shining Armor: Titania does subvert this trope, but the way she does it is really shallow. The whole "Meteor will stop at nothing to achieve their goals, so why should I?" falls flat quickly because Titania doesn't have a goal. She just flails around aimlessly, blaming Meteor for her problems, blaming Amaria for her problems, and doing nothing to help anyone, not even herself. Yes, she was trying to save Amaria, but then what? If Amaria kept her memories, the whole thing would just happen again. And we saw what happens if Amaria loses her memories: Titania, instead of helping her friend, just runs away.
* Incorruptible Pure Goodness: Titania suffers from "Subversive fairy tale rewriting" syndrome. The darkness that she's supposed to represent is never fully explored, so she just comes across as rude and violent for the sake of being rude and violent. Like I mentioned before, her whole speech about paying evil unto evil doesn't hold water because this visionary point of view doesn't go well with her single most defining and consistent piece of characterization: Her short-sightedness. In fact, the main problem with this trope is Saphira: She has the same "pay evil unto evil" ideology, but in her case it's justified: She's spent her whole life protecting her sisters from Sigmund, after all. Titania, by comparison, murders people just because she wants to.
If I were to describe Titania, I'd say that she's quite pathetic as a person. Her short-sightedness always gets the best of her and she has a need to blame other people for her mistakes, as shown with the Meteor grunts, the player character, Florinia and Amaria. She'd be an excellent character if these traits were explored. In fact, I hope that this is where her character development goes! However, her flaws are completely overshadowed by "cool badass sword lady", so much that I had to take some serious liberties with what we've been shown of her to write about them.