Hmm, getting into Isley's head is harder than it would seem but a few things are easy to distinguish. Yes, he did admit defeat - If they would have continued, even with 100+ years worth of experience at his back, Isley would have lost. So he did the best thing, he submitted to the will of an extremely powerful child - a young lady with a child's mind. Nice and soothing promises will calm almost any child down if they will get what they want in the end.
By doing that, Isley placed Priscilla under his control. He's now the one who will fulfill her heart's desires and she'll stay with him and do what he says as long as its towards her ultimate goal, or so he will say.
Same ploy has been used so many times throughout history with a child in power and his 'trusted' vassal, corrupt or upright, guiding them. In Isley's case, this is extremely risky and sneaky but Isley is capable of pulling it off. So in reality, Isley's story that he has the woman with power above the Abyssal Ones in his camp is very true.
As for Priscilla, when she found Raki, she had hit that town a day ago so she wouldn't have needed to eat him immediately. Since he came from the South like she did, all her thoughts, even those of feeding her massive appetite, were pushed back. I see the person she killed in the anime as being an 'emergency ration' since she was probably starving herself being around Raki. Raki is right now the one person that Priscilla will NOT eat and hell will come in the form of a demonic Awakened One with unlimited power if anyone tried to eat or harm him in any way. That and she had probably fed enough in the years before the invasion of Pieta that her appetite would have decreased from the 'ravenous' mode it was in after her Awakening.
Raki can't drive a sword through her heart but his words could have that effect. Like Black Lagoon's Rock, Raki's 'blades' can very well come through his words to Priscilla. If he rejects her, she's going to throw an extremely dangerous tantrum.
Not a light tantrum either like a child in a supermarket wanting a toy - I mean one where the kid just flips out, grabbing and throwing stuff, screaming and becomes a danger to themselves and others. Isley probably doesn't realize that in having Raki there, he's endangering his entire plan to keep her in control. Once she finds out what happens to her parents and her 'memory' returns, she'll flip out - Isley knows this. He's hoping that he'd have enough 'power' to hold her until she calms down and she can start thinking like an adult Priscilla. This will probably backfire in his face because her mindset as Claymore Priscilla is the one that's being repressed. That mindset will NOT be able to comprehend and handle the knowledge that she became an Awakened being and has killed hundreds of people. Her worst enemy is her own self, in this case - a hydrogen bomb just waiting to go off once she remembers everything.
I also find it interesting that even as an Awakened, Priscilla's actions are still 'innocent'. Not morally innocent - she's slaughtering entire towns to feed her voracious appetite - but rather innocent as in the same vein of a young child who finds it interesting to impale lizards with sticks to see how long they move for. We as adults would call that sadistic curiosity and probably punish that child in some way to show that that line of thought carries much more than just simply sedating one's curiosity. Her personality is devoid of the usual man-eating, manical glee that nearly all Youma and some Awakeneds possess. I will even go so far as to suggest that it seems that she's not even aware that she's killing the people who's guts she's devouring. She has to be aware on some level but her current mindset refuses to process it. As with the child - the only way Priscilla will know that she's doing 'wrong' is if someone tells/punishes her. Problem is, who in the world can punish Priscilla?
Isley surely did not do such a thing. He encouraged her to tone it down a bit but he did not tell her to stop at all. In fact, he most likey rationalized it for her so that she could accept it easier.
Scary as this may seem but I still got some more stuff to say but I'm calling it quits. I've got a shower with my name on it.
