Not many choices. Thrush is most commonly caused by a yeast called candida albicans, and needs to be treated with an antifungal agent. I'll assume that she has been prescribed Nystatin liquid suspension for mild oral candidiasis. Nystatin also comes in a lozenge form, and so does another effective drug called clotrimazole. However, lozenges should not be used in children under 4 due to choking hazard.
Thrush=Candida. If Nystatin liquid has been prescribed and your little girl does like the taste of the room temperature liquid, you can try freezing it in an ice-cube tray with the 5 ml measured into each cube space in the tray. Some kids who do not tolerate the liquid will suck on the Nystatin ice-cube.