At this point in the game, I would stop giving treats. Reserve treats to teaching new tricks/behaviors. You should transition to praise or environmental rewards. My shepherd, Buddy, will always hit the end of the leash if I give him full leash. He gets excited from the smells in the environment and he becomes aroused and goes into marking mode. Sometimes I will work on the premack with him on walks, but when I'm not in the mood, I keep him in a heel the whole time. I give both verbal/leash corrections when he steps ahead of me. Give him an inch and he takes the whole length of leash.
When she pulls on the leash, is it when you released her to sniff?
Can you video?