I don't care how, or why, or what other justifications there might be....
Controlling is controlling is controlling....
In the end, nobody has the right to control another human being to that extent.
If I want my own room... I want my own room.
The sister is pretty much expecting other free independent adults to sleep in a room with her, share a bathroom, maybe even a bed... and PAY for it.
Without even 'asking' or discussing. That is just beyond.
And, the whole shunning and ostracization thing... that's a whole 'nother level.
The OP needs to learn how to see and respond/deal with this.
That goes without saying.
If this sister chooses to cut people out of her life, the OP has absolutely no responsibility for that.
But, back to the important topic....
Everything else is meaningless distraction here.
What we are talking about here is a situation regarding the deceased father's affairs/estate.
Unless this sister's name is listed on everything, and every account, as the sole, one and only, co-owner,
A LAWYER WILL BE NECESSARY.
That is just how it works.