Family members visiting when mom or dad moves in.

My mother recently moved in with us, and my sister who has bi-polar disease among other problems, is extremely upset that we will not allow her in our home unless we are there. Now she has disowned me which would be at the cost of not visiting her mother, stupid right? My question today is, would you let a sibling with a troubled past be at your home when you are not at home? Trouble does include pretty much everything. She can visit when we are at home, but Mom rents a room from us and this does not mean that friends/family also rent here, I feel they can visit when we are at home!