Your pup is beautiful and I am very happy you have found a trainer that you have confidence in. I have experience using Prong Collars and E-Collars (shock collars for the sensationalists) with experienced trainers that have titled dogs. One thing I have learned is that not every training method works for every dog be it pure treat based training, positive reinforcement only training, prong, clicker, e-collar, etc. There are as many different training methods as there are trainers, and when used correctly with the proper tempered dogs can have great results.
You have obviously associated the prong with a positive and your puppy is not fearful of it but looks forward to training. This is fantastic and I fear people who only associate the prong with a method of pain are mislead. I have seen many trainers use it as a quick method of communication or shape behaviors much like a collar pop. I dont think many can really convince themselves that a flat collar pop is "painful" but it is an attention getter. I am assuming( which I could be wrong) that your trainer starts the collar early to get the dog used to training on it while doing basic obedience commands. This follows through later as the dog does more advanced commands that require shaping. At that point the dog would already understand the communication that is being delivered with the prong collar to help better shape behaviors.
I think too many people just associate the prong with owners who are struggling with walking a dog. That the only way to use a prong is to deliver pain. This is not the case and just like any trianing tool can be misunderstood and misused. You are not going to "ruin" your dog if you are using a training method properly and your dog is responding well to that method. She is not fearful, cowed, stressed, etc. She performs commands eagerly once she understands what is being asked of her and the training tool is used to shape behaviors not punish.