15 weeks is very young, still a baby. She will pull and there is nothing you can do about it at this age really besides use a good harness so she doesn't hurt herself. Start teaching heel with treats by your side as you walk, rewarding the heel behavior. Timing is everything. After 4 months or so, you can try a waist squeezing no-pull leash. It wraps around their waist area in addition to the neck. If they pull it will squeeze their torso and sometimes its enough to discourage pulling. Later in life, if it is still a problem, you might look into a prong collar as well. Ellie is 1.5 years old and it is still an issue for us, but just not as much. She really does try to not pull, but sometimes we have to remind her. I would just stop if she pulls hard and she knows to come back and loosen up, otherwise I won't move. My understanding is that it is a long process with this breed, they are just natural free spirits designed to run long distances and a leash walk isn't their top choice per say.
My Charlie is 1.5 yrs old and I’m still working with him on a lease to not pull and consistency heal to my side. I’ve found that using a normal collar isn’t good for him as he starts choking himself. I used harnesses with a back ring but he just pulls harder. So I’ve gone with a harness with a front ring and it’s been great. If he pulls I’m able to control him, turn him to the side and stop the pulling.
I am working on getting him to naturally heal. I saw something I really liked which was to put peanut butter on a spoon and let your dog lick it when they are healing correctly. I plan to try it this weekend.
On the front of Sophie's harness is a loop for the leash (on her chest). I hooked the leash on that instead of the one on on her back and the pulling instantly improved dramatically! I can barely hold her back if it is attached on her back.
Once they are older, I always used a prong collar. Funny, but I think it is just repetition and rewards. My first V, we lived in the city so numerous leash walks. I would walk and if he pulled I would change directions. I would walk for an hour and never travel more than 50 yards from my house sometimes. But he got it. My current V, we live in the country, so I barely use the leash. He is a rock star with out it, but on a leash...not so much.
I started to fix this by doing more walks. I'd feed him his entire breakfast on a leash walk. if he stays by my side I feed him without breaking stride. If he gets in front, no food. If he pulls we change direction. At the end...he gets 15-20 minutes to run leash free. It will take him much longer though than my first one who had many, many more leash practice