My mother has glaucoma, allergic to all drops and pills, sight gone in one eye and pressure is 27 in the other, how long before the pressure goes up?

No sure what you mea. Sounds like your mom may need surgery with a glaucoma specialist. Please see one asap. To find a glaucoma specialist near you i would recommend the american glaucoma society website.
IOP TOO HIGH. Unfortunately for your mother, her eye pressure sounds too high already, and that higher pressure for her only remaining seeing eye will result in further visual deterioration. I advise she be evaluated by her eye md for possible surgical intervention for her glaucoma. Good luck.