I have a lot of conflicted feelings too! Mostly along the line of why the hell Merlin hasn't just showed Arthur where Morgana and Agravaine meet ages ago so all of this had been avoided! *sigh* Your idea of at least telling Gwen about magic makes sense too. *sighs again*

I'm kind of annoyed that Gwen didn't get to have her own feelings here. Ok, really annoyed. Why can't she have conflicted feelings? I mean, she clearly was reluctant to move out of her home, she knows it will he hellishly tough to be Arthur's queen, that worry alone could have let to an incriminating scene with Lancelot. I'd have liked that better.
It's also way too clean that they can bring her back and have happily ever after marriage quite easily - with no Lancelot there to mess it up. Humpf.

I agree that Arthur was acting out a sense of betrayal and genuine hurt rather than pride. I tend to watch a lot through his eyes, so this one hurt to watch.

Your thought of where Gwen is is actually heartening.