1 mouse a week is much too small a meal for her. Can you get a hold of rats? A weaned or small rat would be the prefect size for her. You would only need to feed one rat a week to her. If you can't get a hold of rats, trying feeding multiple mice in one feeding session (at least two...three if she'll eat it).
As far as the temps, what are you currently using to heat the cage? UTH are great for creating a 88-90* hot spot (but it must be hooked up to a thermostat). If you are more concerned about ambient temps, then you can use a lamp on a dimmer (you can get these from places like Home Depot) to make sure that the lamp isn't getting too hot. Another thing you can try is covering most of the lid with foil. Not only will this help to trap in heat but it will help with humidity levels too. Even though you didn't mention humidity levels, there are ALWAYS humidity issues when tanks are involved.