I have checked the rule on Web, I'm not sure whether it's too simplify. It said she need to have a private place to sleep and can't together with a male after x age. i.e. can't sleep in the corridor. Thus I think at least a room with door. but no need to cater whether the bed is fixed or not.
I heard an extreme case from my husband: one of his friend (direct friend not friend's friend's friend) living in small/medium size unit and his maid sleep in floor of kitchen. Yes, not even the floor of living room but KITCHEN.