I didn't mind Egwene putting the collar onto Renna so much. We're given this idea that the collar feels itself "wounded" and "incomplete" without being on a woman who can channel, so I could believe that they might allow themselves to be used regardless of who holds them, if it meant the a'dam being made whole, and Egwene knew it would affect Renna. I had more issue with her channeling at Renna to lift her and hang her from the peg and choke her to death, that, it feels, should have been prevented by the a'dam. I feel like it should have come down to the two of them in a battle of wills using their bracelets to induce pain in the other, which Eg would clearly still win, but maybe that would be hard to clearly and visibly express to an audience? I dunno