Is a bun/ratio of 27 considered high if bun and creatine measurement are within normal range?

Of little concern. Bun/creatinine ratio is of little to no importance unless a physician is looking for an explanation for a person being in significant kidney failure. An older healthy woman is likely to have a lowish creatinine anyway and if you like to eat meat, this raises the bun. This is all harmless. Look at the person, not the numbers, and if your phyiscian isn't worried, forget it.