Kate.
I see the prize money as a reward in what is basically a personality contest - rewarding Jade for her behavior would not be a good thing. Although I do hope this experience helps her to make some changes in her life, letting her win would be a green light for her behavior in the house.
Jonny whinges too much (sorry), and Alex had a part in the Sophie- bashing too. Of course, if Kate goes tonight, all my predictions are worthless anyway..........