Is it normal for a 15 year old to have a heartbeat of 86 beats a minute?

The normal heart rate for a 16 year old female would be between 60-100 BBM. 54 BPM in a resting state is not unusual. A healthy athletic female may have a lower blood pressure and heart rate than a non athletic female. This is due to the heart being trained, so to speak, in being more efficient.