I agree with Susan, 1 fuzzy every 7 days simply isn't enough I'm afraid. Do a search on the forum search engine for 'Munson Plan', as Janine said. This is a detailed feeding schedule that gives the right size mouse for the snake's weight. I'd have a look at this, weigh your snake and go from there. But I'd give a relatively small hopper, just so her system can adjust to the change in size.
About your heating method, reptiles can see light, but red lights don't bother them as much. Are you using a standard incandescent lightbulb or a red bulb? Because snakes can't see colour, at least not like we can.