When you reinforce her after the release, you are actually reinforcing the release, not the down or sit. When you give the down or sit command, click and reinforce as soon as her but or elbows hit the ground. Keep reinforcing with food as she sits or downs for a short while and then release and praise and do an engagement spin by luring her with the food and reinforce the spin with a bite of food.. The spin will be more difficult if she doesn't have a lot of drive. Then do another sit or down, click as soon and she sits and reinforce, etc. You need to do more continuous reinforcement when a pup is learning a new behavior and people underestimate the large number of repetitions and sessions it requires to get solid obedience. Don't just train before meals, but train as meals some. If you use real meat, she will get adequate nutrition. If you feed kibble, you can either cut back the amount or cut back on the number of times a day she eats. Regarding the ball, you are much better off using a ball on a string rather than throwing a ball. With a ball on a string, you can tease her with it by giving her misses, building frustration and drive. It is a skill you have to learn and the dog needs to have enough drive genetically for it to be a useful tool. With the ball on a string, you can also tease her up and if she comes into drive for the ball, give her some misses and put the ball in your pocket so that she doesn't get it at the end of a session. It doesn't sound like you know how to stimulate her prey drive. A rug tied to a buggy whip properly used can help build drive. But again, you need to know how to use it to be effective. There has to be some teasing and misses when she goes after the prey object in order to build frustration which builds drive. The way the prey object is moved is also a factor. With a rag, use short, quick, jerky movements. I don't know your dog's breeding, but for higher level obedience, you want a dog with high prey drive so you don't have to do so much "begging" with a toy.