Currently, it's nothing to worry as platelet count is not alarming as per dengue positive report. But, platelet starts to decrease only once the fever disappears. So, you have to wait and monitor you child even more once she is having no fever. Watch for any rash, her urine output, any evident swelling over body or any discolouration of urine /stool, vomiting, stomach pain, breathing discomfort.
Keep her hydration proper by giving plenty of fluids orally.
Next Steps
keep a close watch on her once she is afeberile.
Consult pediatrician immediately if any doubt.