What is considered high blood pressure for an old female?

Depends on how old: Optimal blood pressure is under 120/80. Risk for heart disease and stroke begins to rise at 115/75. The elderly are "allowed" a bit higher blood pressure because the arteries may be stiff and not tolerant of 'normal' blood pressure. However, if well tolerated, it's best to stay under 120/80 for life. Allowance in the elderly should be considered by your doctor based on your health.