My 77 Year Old Sister Is In A Nursing Home.

My 77 year old sister is in a nursing home. She has some dementia and other problems. She has been a little combative and uncooperative lately and they want to up her dosage of Zyprexa from 2.5 mg once per day to twice per day. On the internet I saw that the initial dosages begins at 5-10 mgs. How safe will it be to raise her dosage. I am also her legal guardian and they need my permission to raise the dosage.