I have no complaints with the way Crest is handling this "revelation." It's perfectly in character for him, and pretty much for ANYONE who would get blindsided by this.
I DO have complaints with how the phalanx are acting. This is seriously NOT in character, especially for Q'talda. In order for the phalanx to be there at all there had to have been numerous high level correspondence between the phalanx and the knights, as such, Orangsong should have informed the Crest household that they were looking for him, and why.
Instead, he's ambushed by someone claiming to be Q'talda, and stating things completely contrary to what Crest, as an eye witness, both saw and heard during the Conclave vs Suspira.
I'm completely with Crest on this, this is just too out of left field to be believable without additional proof. Can Suspira's parents actually prove they are who they say they are? Can Q'talda?
Everything we've seen about Suspira's behavior prior to the incident was clearly provable. That girl posse she assaulted DID bully her, and in front of witnesses, which adds to her credibility.
Yeah, this is going to be a tough sell, Q'talda.