I don't want my mom in my dad's hospital room
Why don't you want your mom in your dad's hospital room?
She keeps acting unpleasant towards other people
It is not your business and you should not prevent your mom from being in your dad's hospital room. He may be happy to see her and it is not your decision to prevent that from happening.
She wants to see my dad die, it's natural she's happy. I am going to counteract her plans.
Well she has every legal right to be there and it is your fathers decision. There is a thing called power of attorney and marriage would give her the first in line if he doesn't have one. Just try to be there for him as he dies and not create drama.