I mean, this is only going by my interpretation... I may be reading too much into it/going too far, but

What is an oath to a bladesinger? Why are their oaths so precious and important to them?
Each one held, each one fulfilled, they temper their resolve, strengthening their will, their heart, the strength of their spirit
The power in their song
Half of the song is in the steel blade they wield, the instrument of battle that sings in the air it cuts through
The other half comes from the wielder. To join their spirit with their blade.

I don't disagree that she could yet retain her class and features... but the main problem that arises is the fact that even if no other were to call her an oathbreaker, she is severely shaken, traumatized by what she couldn't prevent.

As a leader, she carried the weight of responsibility. All decisions effectively put to action by her approval. In this adventure, not a single one of her decisions has led to a good outcome - a moment of passion leading to naive and ill advised trust, the night in the forest a result of her overconfidence, the battle thereafter lost by her poor leadership, her choice of literal path in the temple that saw to the party's defeat and capture, and then at the very end, her very inability to put an end to it all. Her lack of strength to grant them victory from absolute defeat, rendering her gambling with the others' lives fruitless.

In the unposted in-between, she was literally an inch from taking her own life...

After all of this... from where can she find the certainty, and strength, to sing again?

No doubt, the pet cat KILLED me. 

For the record - if you want to get really, really technical, Davena is absolutely, 100% a victim, herself.  She is 100% batcrap crazy like Kith is.  Had she not been taken as a teenager, she's be a priestess of Miellyah now, helping deliver babies and bless crops.

As much as I'd like to eat that slitch, myself, you're probably right... If there's a way to "fix" Kith, who's to say that Bae-vena can't be helped, as well. I mean, she's been in the game for quite a bit longer, so take what it might take to fix Kith and multiply that by the nth degree... Who knows?

Also, what are the hypothetical ramifications of Kithy's "murder baby" being born but killed afterward, I wonder? Been having some back and forth with Bree and Rer regarding the aftermath - what happens with Ara, etc - and one possibility take Ch'dau and Aranwen out of the picture for a month or three, most likely. I mean, supposing that Ch'dau takes Ara away, the two settle down in some remote village, mourning the loss of their daughter and then, some time later, Gib and/or Cedric show up saying; "Hey! We've got an idea of where Kithran is. We can still stop this!"

P.S. I'd be Aranwen's pet cat ANY DAY!!!  

Oh, Gib would have definitely spent time researching the "incarnation" angle to get as much information as possible. Also, Reralea, one of the most fun characters I ever played was a fallen paladin who had to earn back his paladinhood. FYI - he only did so posthumously. He died trying. Still, it was a really fun playing experience.

I think that you are very spot on with the strength of the bladesinger and their oath.  

A few observations:

There was no way to know which path would lead to disaster in the temple. 

Aranwen saved the party with her surrender.  Garrack would have let the ghouls kill everyone.  Where there is life, there is hope.

These battles were lost, yes.  But had she not made that wise choice, everyone dies.  No one knows of the conception of the death god's spawn, who is able to be born in secrecy, rise to power and end all of reality unchallenged.  As it stands now, the party can regroup, warn their organizations, proceed to search for Kith and end the threat.  Perhaps they can redeem her; if not, they can at least save everyone else. 

I think that some time with a priest could perhaps make those truths clear.  Perhaps Ara could draw strenth from that purpose, that redemption.

I thinkt hat a break of a few months to research and figure things out, find a way to scry or whatnot, makes so very much sense. 

And, to quote the man, himself; "I wonder if these characters know just how real they are?"

Oh, and Gib doesn't blame Aranwen at all. He's been the advisor and he screwed up too. Guilt is weighty.

It's probably good that they don't know how real they are.

I do believe you've given Aranwen one reason to be in HC2 at the very least

Technically speaking, we already do have a 'lead' that could help locate Kithran - Aranwen's dishonoured blade. If there's something like locate object in divination, Aranwen's innate familiarity with her blade of thirty one years could serve as the focus and conduit of such a spell.

That was QUICK. 

Smart players make a DM's job so much more challenging.  And amazing.  And frustrating, .

I love the idea.  Some time to learn what needs to be learned about this death god spawn.  Find a mage who can cast such a divination (sounds like a trip to Felarin might be in order?).  And off on an adventure to save de world...

Get over here Ara!

Let's electric bugaloo!

And six more levels have been gained apiece in the process. All right, Olan. If you insist. Twelve. Twelve more levels. I know, I was being stingy. Thanks for setting me straight, my friend.

Sweet! that give ch'dau plenty of time to train and specialize with a battleaxe!

U da MAN, Olan!

Tee hee.  I love funny jokes!