My sister is in nursing home. She isolates herself in room. A resident in wheelchair comes in room and she basically chases them out.

Be glad She protects herself. Be glad she does that instead of letting some jerk in to rip her off. My daughter wants me to be sociable. I had sociably I don't need sociable now 81.
My daughter's 40.

Can she Lock her door with a key?? As long as she's in her room no one can rummage thru it including staff. Homes don't/can't screen for honest trustful staff and inmates/patients. I mail ordered an extension charger for my device. If I didn't get notified of delivery an employee would have got away with the theft. Got notified no delivery went to mail room, they said Dave's back at the Dock got after checking, brought the package back to me opened and asked is every thing there. It was. Reported to Head Administrator head nothing likewise on other things It assumed patient don't need to be listened to by most employees. When you visit observed their behaviors acting out laughing like recess time detached from their surroundings. The employees.

IMO, leave her alone. It could be depression and maybe pills would help. But if she does not want to interact with people, thats on her.

Why should she come out of her room if she doesn't wish to?
Seems you are trying to manage her social life?
Why should she allow anyone to enter her room?
I am 81. Were I in a facility that would be bad enough, but I sure would want my privacy.
And as someone basically never very social the thought that people could come in and out of my room at will would make me quite frantic.
Please allow your sister to manage the end of her life without your input. Be supportive of her choices.

Is your sister on an antidepressant ?
Depression is usually a given post stroke .

Is there an activities director at the NH? Perhaps address this issue in the next care meeting you have with her team.