It's clear that Wanda uses some sort of spell on Jillian; she cast it on page 30 and if you look closely you can see effect sparklies around Jillian's head on page 36. That said, it seems unlikely that the spell was some sort of overwhelming "mind control" -- if she had that, she wouldn't need to bother with anything else. The most straightforward interpretation is that it was something that "softened up" Jillian for Wanda's other methods.
That said, I agree that Jillian has formed an emotional bond to Wanda as a result of Wanda's working on her during previous captivities. I see her "let's both of us get out of here" as a result of that (though not at all the result Wanda was looking for, obviously).
I agree that Jillian's "crash" on page 38 is probably sudden realization setting in -- the question is why this happened suddenly at the moment of the dawn "reset" (note that the rations popped and her wounds healed at the same time). It seems to fit the notion that the spell had left her muddle-headed and suggestible, it expired at dawn, and she was now suddenly clear-headed and aware of what had just happened. If Wanda expected that outcome (and presumably she knows the effects of her own spells, even the boring old non-Croakamancy ones), that might be why she described it as "the very hard way".
Unfortunately, it's hard to tell if the "sparklies" are there in page 38 frame 2; they're definitely absent in frames 3-4. If they are, that would pretty much confirm that the spell expired at that moment.
I commented at some length on my interpretation of Wanda's initial comments to Jillian in the thread "When Prisoner Says 'The Easy Way'".