Actually, she admitted it was amazing in the next breath after she said she never wanted a repeat. Rather like Pearl's post-coital attitude after the intervention of the crystal.
My first impression of Amy and Hayley's charade game was that it sounded like a way to share pleasure, grow or test their bond, have fun with a bit of a shared inside joke, and develop a "nuclear option" for ending the relationship if it ever soured.
And for bonus points, I focused on the negative outcome--something exceptionally unlikely because Amy has been conditioned not to be jealous.
Taking another look, I must admit I'm exceptionally curious. In the past, Adrian has accepted change of heart as explanation for a behavior change. He might be less likely to do so now, but that's not clear one way or the other. It should be fun finding out what the Twins have planned.