Is it normal for a 23 year old female with perfect blood pressure to have a heart rate of 120-140?

No. it can be normal if you are actively exercising, but not normal if you are at rest. See a doctor, as you may need testing. Hyperthyroidism should be ruled out.
Tachycardia. A HR of 120-140 is on the high side. Would check thyroid studies as hyperthyroidism can cause this ,would also check for autonomic dysfunction as in POTS syndrome( tilt table test), avoid caffeine energy drinks,alcohol, cocaine as that can raise heart rate. Would check echocardiogram and 24 hour holter. f/u w/ cardiologist http://www.mc.vanderbilt.edu/root/vumc.php?site=adc.