I think going to bed before your sister gets home is a great idea.
Next time you feel tempted by the KFC distract yourself. Go for a walk, call a friend, write down how your feeling, have a glass of water, etc...that's what I do when I feel tempted and it happens alot! My fiance loves junk food (tall and slim man
) and last night he ordered pizza. I kept to my food plan but the smell of the pizza and cheesy garlic bread was getting to me so I made a cup of tea and went to another room to watch TV. This morning there was leftover pizza in the fridge so I put it on the bottom shelf, out of the way. It looked all yuck and greasy so i'm glad I didn't have any last night.