If your BP as been refusing food for the past couple of weeks and has decided to stay on the cool side than that is his/her preference. The reason we supply a hot and cool is to ensure they can be where they want. If she ate a meal I would think she would need the hot side but while not digesting she could just prefer the cool side for now.

If you see no signs of illness and the only issue is you think she's been on the cool side to long then just take a deep breathe and let the snake do what it wants.