Just a couple of other thoughts/considerations to what has been offered. If you have already implemented a positive and negative marker or marker word to what you have already trained her and that she understands well, have you implemented that with the loose leash training? If you have, and she understands the concept that you don't want her to pull, then it is fair to give a collar pop correction. If she does not understand, then you need to go back to basics.
My guy absolutely understands that he can't pull. He proved it one day when he started pulling. I stopped and instead of a collar pop I just waited him out. He stood there with a tight leash, waiting for me to move forward, when I didn't he backed up to relieve the pressure, when I still didn't move, he backed up more so the leash was nice and loose. Bingo, he understood just fine what I wanted and expected.
Another consideration that I don't see expressed on here much is length of natuaral stride and how yours and his fits with each other. My boy's natural easy going walking stride, for every one of his, it takes 1and 1/2 of mine so either he has to slow up or I have to quicken. It took conscious effort to find and keep a comfortable unison pace and a lot the forging that he did was not conscious disobedience, just his natural stride. Our previous girl (a mix and much smaller) had a natural trotting stride that matched perfectly to my walking stride. The loose leash concept was a breeze to teach her due to her stride. It is different to pulling to get to something quicker but just another thing to think about as you work this out.
Like others, get a trainer to teach you what a fair prong collar correction is and how to administer one.
"If you can't see his soul when you look in his eyes, then you need a seeing-eye dog"