I think "good girl" has become a release word???

I have a 6 month old puppy. She is a good dog and is doing well with training. I mostly just do positive reward based training, but I don't always have treats in my hand. I try to tell her "good girl" as a positive marker, when she is does her tricks or when she is doing something nicely, like walking loose on the leash. But now it is starting to seem like if I say "good girl" the trick or whatever is over, and she starts doing whatever she wants. On walks she will be walking nicely, i try to praise, and when I do, she goes ahead and starts pulling. Obviously I will still be using "good girl" along with the rest of the family and most people in the world, so is there a way I can add in a real release word or teach her that "good girl" is a praise/reward, not permission to do what her puppy heart desires???
ps. I am a first-time puppy owner, but have read every book and website there is and have been lurking on DF for years....so I hope you guys can give me some solid advice to help with this, it's not a huge problem, but I have no access to classes or trainers where I live and I want to do my best with this pup. Thanks.