I have several that will sit and quiver right before striking. That doesn't mean I am saying there is nothing wrong with your snake. I am just saying it sounds like an aggressive feeding response to me. You need to keep an eye on her. Try prescenting again before feeding and see how she acts. The best way is to let the mouse thaw, warm it, and let it sit on top of her enclosure for 20-30 minutes. Or atleast close to the enclosure. She will get the smell and be ready to eat. Prescenting will almost always get you a better feeding response. You still didn't describe your enclosure.