You should not try to feed every night she is out. Your snake is best served by a schedule. I would recommend a mouse or rat that weighs around 10% as much as your snake fed every 5 to 7 days. If your snake refuses a meal you wait and feed on the next scheduled day. This allows your snake to refuse a meal for whatever reason without you stressing her out. As your snake gets bigger you can scale down the size of your prey and go longer between feedings. I go for about 5% of my snakes weight every 10 days. My BP is about 1300 grams now.