If the owner of a business is in a coma, can his estranged sister take it over after only 7 days?

My friend was in a car accident a week ago and he is in a coma. He owns a mechanics shop and recently bought a house. He has a girlfriend, of 3 years, who is trying to take care of everything, but his estranged sister heard of his accident and is trying to take everything. Does his girlfriend have any rights? His sister is also trying to kick his girlfriend and 3 kids out of the house, so she can stay there. His sister is just looking to make a buck, from her brothers accident. Is there any help for his girlfriend?