Fever with cough and a fast heart rate in a child can happen with infections like Viral Fever, but you should monitor her closely. Give Paracetamol in the correct dose for fever, keep her well hydrated, and ensure rest. Check her temperature regularly and keep her in a comfortable environment. If the heart rate is very fast even when fever reduces, or if she has breathing difficulty, persistent high fever, vomiting, or becomes drowsy, seek urgent medical care as soon as possible.