i'm not a medical professional but I can say this because I have my grandmother with dementia and she behaves the same way except the danger part. The biggest virtue that is needed here is patience. You need to understand that that person is suffering a severe neural disease and need to think from her point. Next, handle her with love and care. It will help if you can get someone whom she knows very well or atleast used to know well, like a relative or a close friend and ask for their help.
I have noticed that my grandmother listens to me more than my neighbour so for the same reason i advice you to get her someone she knows.
Good Luck to you.