If your vet has indicated there is no health problem (like HIP DYSPLASIA) which would make walking esp on HARD surfaces more painful and the dog does not have overgrown nails, then do plan to "reward her" by putting a HIGH VALUE TOY (she LOVES or she will love maybe w/ a squeaker) or a HIGH VALUE treat out, ahead of time on the walk route.
When she finds it, make a BIG TO-DO over it and give her a chance to play with, or enjoy it.
I had a friend try motivating her dog to track, by putting out an unopened can of MIGHTY DOG (the ones that come in a small pull-top tin-size) at the end of her track and the dog got NO breakfast until it got to the can. BINGO!!!!! Yummy, canned dog food, instantly opened, or already open. It worked REMARKABLY well!!!!