Crowley
Yes, I did some research on your...specialty...today. A soul for Hell as I understand it. I also understand I won't have officially made a deal until it's formally sealed somehow the books said a kiss but that would be rather so these are all preliminary negotiations and non-binding, yes?
So, in that spirit, my sister suffered some trauma a year or so ago. A group of people cut into her brain, implanted memories and information, stripped her amygdala amongst other things. Could you restore her to her condition before that? Make it as if it had never happened? Also, and this would be an essential component, you would agree not to make any deals with her.