Make a chart and put stickers/stars/checks on it and a certain number of stars will earn her something (based on how long you think she can wait)---still a treat, but takes more time to earn, so it's not every time, but always praising (sincerely, not exaggerated, kids can tell when you fake your enthusiasm). Then, after a while you can raise the expectations again, and eventually find something else to focus on--- In other words she mastered the potty, she can learn a new skill because she is a "big girl". When she is mature enough, gradually switch to just praise, not external rewards.
The idea is that she should learn to be intrinsically motivated (from the inside, for a sense of personal accomplishment), instead of extrinsically motivated (thinking nothing is worth doing, or has any value unless it comes with a "prize").
It makes me sad that good intentioned Granny gave too many prizes to my (step)kids for so long, that when we praise them for good behavior and tell them how proud we are of them, the youngest (9) will still ask us "So...do we get a prize??". We always tell him he JUST DID!---that having people think good things about him, and enjoying him, and being proud of him is the best prize he can ever get--much better than a piece of candy or a plastic toy. Someday, hopefully soon, it may come to him that we are speaking the truth...