Size is not all that indicative of power. Sometimes a large dog is actually laid back and not much of a puller. And sometimes a little drink of water at four months old can drag down a kid.
Start now, get out there every day with the dog, go to classes, and just keep on going to classes, and TEACH the dog how you want her to behave on a lead. She can pull, but you don't need to follow. Dig your heels in and wait for her to realize you are not going her way. Or turn and go the other way. Teach her to pay attention to you, and go your way.
Don't wait until your pup is 18 months old and 110 pounds and pulls you into a jogger to decide whether you should get training, or rehome her, or let the authorities take her and dispose of her the way they would most likely.
Jenna, RN CGC & Babs, CD RA CGC HIC
Heidi, RA CGC
SG3 Odessa, SchH1, Kkl1, AD
Ninja, RN CGC & Milla, RN CGC
Joy, Star Puppy, RN CGC
Dolly CGC & Bear CGC