Hello, I understand your concerns. The duration of action for tylenol is only about 4 hours and the fever will recur until her body is fighting the virus. If she is feeding okay, and is active when she does not have fever, it is not concerning. Warning Signs: 1. She is lethargic and drowsy even when she doesnt have fever 2. She is refusing feeds 3. She is peeing less than once in 6 hours 4. She has fast breathing 5. SHe is irritable and crying continuously If any of the above are present, take her to a pediatrician. Otherwise, the fever should settle in another day or two. Has this answered your question? Hope she gets well soon!