not entirely random SWTOR thought...
...following a chat with dareva about those sound files, you know which ones.
What if the reason (or one reason) why Quinn is so flustered around the female Sith Warrior is because he's actually (mostly) gay, and is surprised to find himself attracted to a woman?
As I've mentioned before, it seems to me that he'd likely be bisexual, given that most of the reasons he's attracted to the SW are non-gendered. Loyalty, honor, decisiveness, a strong (dare I say dominating? *smirk*) personality, combat skill, and the aura of power and mystery associated with being Sith all seem to be in there, but as dareva noted, he never really says anything about the SW's appearance. And (mild spoiler) in one of the early dialogues, if you choose the right option, you can get him to say something about how the SW is "a unique sort of woman". So, given that the Empire's military does seem rather male-dominated, I find myself wondering if he might just not have encountered a lot of women with the characteristics that attract him?
(Of course, given that he's also very into propriety and the chain of command, I expect the ratio of frustration and unspoken crushes to actual sex in Quinn's life would still skew way to the left...)