Hello and thank you for using HCM.I carefully read your question and I understand your concern. You should not worry about. I will try to explain and give you my opinion. You should know that normal heart rate ranges between 50-100 beat for minute.When it exceed 100 we talk about sinus tachycardia. There are different causes of sinus tachycardia. Simple emotional stress, excessive coffee consumption or pathologys like anemia, hyperthyroidism, electrolyte imbalances, cardiovascular anomalyes, active infections or hormonal changes. When a person experience tachycardia its normal to feel anxiety, palpitations, difficulty in breathing deeply, dizziness. If I was the treating doctor I would recommend some examination like a cardiac echo to evaluate heart function and valves, a full blood analyze to exclude anemia, hyperthyroidism or electrolyte imbalance and a holter rhythm monitoring to evaluate mean heart rate during day and night. Only after this we can be shure if is something to be treated or just a stressed period or hormonal changes that soon will pass. Hope I was helpfull. Wish your daughter good health. Best regards, Dr.Ervina.