I think this may contain a hint to what's going on. Ball pythons are by their very nature ambush predators. They need to wait for their prey, they need to set up their strike from a safe position, they need to hunt (even if that "hunting" behaviour is simply striking at an F/T on a set of feeding tongs).
When you remove her like right before feeding/introduction of her prey you are interrupting the process and likely throwing her completely off her game. Try changing your routine. Watch for her to be lurking out of her hide watching for prey. Introduce the f/t prey on your feeding tongs, give it a bit of a wiggle to simulate live prey and she should likely strike at it. At that point, walk away and leave her to settle down and eat. Do check back about 30 minutes or an hour later to see if she's consumed her food.
Remember that the time when a snake is swallowing a single prey item is a very vulnerable time for them. With their mouth so full they can neither easily fight or flee a predator. If you disturb them during this moment by hanging over them or allowing a lot of noise or vibrations around them, they may break off the feeding.
Lastly make absolutely sure the mice are properly thawed and warmed to blood temps. Some people find that after defrosting and warming f/t prey, a quick blast with a hot hair dryer can help promote a good heat signature on the dead prey and encourage the snake to want to eat it.