A few different things can cause sudden changes in behaviors. She could be in pain or have a health issue going on. other times it could be an dominance issue. She may have stopped seeing you as alpha. But when there is a sudden change in behaviors like this. A vet consultation should always be the first step to assure there is no major health concern.

Puppies can be more expensive because they are untrained on a leash. So they can pull, walk in front of the walker, trip them, stop randomly, try to chase things, Etc. This causes the walk to be a lot more effort than it would be to walk an adult dog. whom you can get from point A to point B without any distractions.