Depending on the age of the dog, you want to limit how long a walk is, especially if you have only sidewalks to walk on. Sidewalks are very stressing to the joints, and can cause splaying in the knee joints if they are walked, or run too much on that hard unforgiving surface.
Certainly let her romp as much as she wants in a park, or other grassy field type areas, but until her joints close, cement should be carefully monitered.
If she as an adult, still moniter how much she is on cement, or pavement, especially when it is really hot, or really cold, but you can walk her longer on those surfaces without too much concern. I let my dogs walk on any grassey areas we encounter on a walk.
For a small dog, a couple of miles a day, spread out, is a good amount to keep her fit and happy. Interactive play, and training time, can further wear her out every day.