How aggressively should a high total cholesterol (say 250 and up, be treated iin 85 yr. Old woman, otherwise in good health?

Good question. Treating cholesterol aggressively makes the most sense for people with high cardiovascular risk. The question i would ask is: how much would this woman benefit at this point in her life if she has no signs of cardiovascular disease? Statin therapy can be expensive and cause uncomfortable side effects and rarely serious reactions. A healthy diet and aerobic exercise have no down side at any age.
Depends. It depends on your other risk factors: smoking, heart disease, hypertension, diabetes. You could have one or some of these and be in "good health". If you have no other risk factors, diet and exercise are important. You are in a high risk age group for cardiovascular and cerebral vascular events and primary prevention with a statin is reasonable.