Dear Lisa,
You bring up several concerns here. First, the normal resting
heart rate range for an 8 year old is 80 to 130, or so, so a
heart rate of 120 is not overly concerning. However, if she truly is anemic, that can cause the heart rate to go up. And, if there is anemia, it would be important for her to be evaluated by her primary care provider to look for a cause of her anemia (rather than just presumptively treating it).