If you’re pulling your f/t mice from a box it sounds like they might be coming from a pet store. If that’s the case, I’ve seen some pretty icky pet store feeders too, and you should consider finding a local or online supplier. My f/t feeders always look healthy and robust. If you want to stick with feeding live that’s certainly an option, it wouldn’t be the end of the world, but it’s usually a bit more expensive than feeding f/t and you may have to feed small-medium rats, or 2-3 mice, per serving. If you really want to transition her to f/t it may take some time and tough love. I’m a firm believer that the hunger always wins in the end and have adopted more of an eat or starve philosophy with my snakes. I’ve had a few stubborn holdouts, BPs being the worst of them, which is a major reason I don’t keep BPs anymore, but they ALL eat eventually.