Mom recently passed, sister with OCD lives with Dad? She does not understand Dad's dementia. What do I do?

My mother passed away in March after a year of being in and out of the hospital seven times and Hopsice twice. My father has Parkingson's. My sister who has OCD lives with my father, but she really is just a body in the house to make sue he takes his meds and eats. I am POA and go on Friday's after work and stay until I have to go to work on Monday morning. I also pay all of the bills do grocery shopping, take time off from work to take my Dad to any and all doctor's appointments as I did with my mother. I also cook and do laundry on the weekends. My sister does not handle my father's demnetia. When my father gets in one of his moods that he is going out or to work, etc. She losses it. Screaming and saying mean things to him. I've tried to explain to her about dementia. I have even printed things off of the internet for her to read and try to understand. At this point I am burned out and my health is not good. I would like to put my father in a nursing home but my sister does not want me to and when my dad is at himself he does not want to go. My sister will have to come and live with me, because she has no where else to go. Any suggestion how i should handle this. I'm really burned out after the year we had with my mother in addtion to being afraid on the health report I am going to get from the doctor my next appointment.