Is a systolic blood pressure in the 120's and 130's considered too high?

Not too high: American Heart Association(AHA) Guidelines Systolic Diastolic Normal 160 >100 Stage3 >180 >110

Above optimal long: term but many other issues. SBP read from only single heart beat, DBP from lowest between two other beats, thus just momentary values which change quickly. Sitting, relaxed DBP typically 40 mmHg below SBP. SBP ~110 mmHg (& lower) considered low normal & usually correlates with better cardiovascular health long term. However many other issues: optimal NMR lipoproteins, HbA1c, etc., more important.

No: I would not worry if your systolic bp is remaining in the 120s. 130-139 is considered to be "pre-hypertensive" so if your pressure is consistently in the 130s I would look into more regular aerobic exercise, and the DASH diet (google it) to help lower your BP.

No: However for a young female would prefer less than 120'systolic is preferred. One reading is ONE reading, so. Do several over several days and sitting, lying down etc to get a good track.

OK for now: Many things affect blood pressure including diet, weight, exercise, anxiety, stress, and other diseases. It's never too early to work on a healthy lifestyle to keep your blood pressure low. What is considered OK today may be considered too high tomorrow! Diet, exercise and stress reduction. No smoking.