So it was purely an Edward scheme that he coerced them into. I'll admit, I'm mildly disappointed in Kate for getting a little too comfortable too fast with her progress and not anticipating at least the possibility of Edward mixing things up with new schemes. It's reasonable to argue she's still indeed a child, and while very mature for someone her age she lacks the raw experience that comes with age nor anyone to teach her at an accelerated rate. Anthony is being extremely damn useless for all his big talk! Even so, Edward has made his animosity very clear and he's still in charge and still holds a dominant position when it comes to power. She should know that if anything the progress she has made actually makes things more precarious, because she simultaneously no longer has full "stealth" so to speak, where everything appears normal and they're operating under the radar, but also is far from ready to simply make a play for freedom. So she should guess that Edward is going to be a permanent, and scheming, enemy until he's eliminated. I'd sort of thought maybe this would combine a trick with "we need to buy as much time as we can" but it appears she was just purely caught off guard, the only silver lining being that intentional or not this definitely is likely to suck all the Adults' focus, and Edward will probably be smug in his out maneuvering Kate. That makes it far less likely for him to expect any other scheme on her part since he too is likely to relax in a "victory", and thus the rescue is more likely to succeed.
Still this is quite a challenge. It's not officially to the death so both can survive, but Kate can't afford to just throw the match either, nor is interference trivial given all the powerful Adult observers as well as extra Edward agent. Looking forward to seeing what they do (and guessing at possible approaches)!