Shrug, MY warrior blamed Baras before she blamed Quinn. You know, the fellow with absolutely zero force abilities or power enough to resist the will of a Sith Lord. She was actually bummed at her own inability to protect Quinn from Baras' manipulations, in fact. It's just that the last person she was truly angry with, was Quinn, who was, she knew, nothing but a mere force-blind Imperial caught between two battling Sith.
So her rage was directed towards what she knew was the proper target for it. Not Quinn but Baras. Which was probably good in the long run, because Quinn is perhaps the most valuable companion she could call her own. He captained her ship, navigated for her, proved to be a technical AND tactical genius time and again, ran her medical bay with expertise, and, finally, helped her relax during downtimes between missions.
You don't ruin something worth having, basically.
The problem is, this spin on things isn't so much of an interpretation as it is head-canon. Quinn was not being forced to do anything. He honestly thought siding with Baras was the best thing for the Empire, and more significantly, for Quinn's career. He thinks he owes his career to Baras AND he thinks Baras is going to be the next Emperor. He just wants to be the Emperor's right hand man, which is as high as a non-force user can go in the Empire. The dialogue in the betrayal scene spells out his true feelings very clearly. Basically, he's an ambitious little weasel and incapable of feeling anything very deeply.
You may also want to look for youtube videos of his comments to the other companions in that scene if you happen to bring them in. Very telling.
No, he's not worth keeping, sadly.
Personally, I adored the character when I thought he was what he appeared to be, a loyal, competent Imperial. Had I been the writer, I would have had Quinn drop you a secret message before you go in. "I'm going to betray you. Baras is watching. Let's put on a good show, eh?" Boom, problem fixed.