Quote Originally Posted by 3SecondCultist View Post
I'm sorry, but I don't feel like that is a valid question. My feelings towards C are deeply ingrained in who I am: we've been dating for long enough that she is one of the most important parts of my life. Our history means that I'm not going to be able to rationally weigh how I feel about her in the scenario you've described.

Furthermore, V has a committed boyfriend, and they've been dating almost as long as C and I have. Hell, I've met him, and they seemed pretty cozy. So in this exercise, I would of course always pick C - but the experiment itself fails because I'm not really looking to swap partners, or compare the two. My problem is not that I want to be with V, but rather how I feel about flirtations that have already happened.
Couldn't disagree more regarding the validity of the question - but you totally answered it in your post.

Which should settle it - you did nothing wrong. As Xapi pointed out, everyone likes to feel desirable. There's a huge chasm between harmless flirting and actually cheating.