Is blood pressure 108/80 good? And how low of a blood pressure too low?

That's fine. Young females tend to have lower blood pressure. Some people may have blood pressure's 90/60 and feel fine. The main concern is the development of dizziness, weakness or fatigue. Occasional dizziness with standing may be normal, as long as dizziness passes within a minute or so. Go to er if passing out, or persistent dizziness.