Why did Anne share a bedroom with Mr. Dussel, a middle aged male stranger, instead of her sister Margot?

This is actually inexplicable......... Anne and Margot had shared the room before Mr Dussel arrival, but after his arrival, Margot moved into her parent's room, and Mr Dussel moved in with Anne. The only opinion I might throw in...... Margot was the older of the girls, therefore it might have seemed to the other adults in the house that her "older" age might have marked her as compromised had she slept in the same room with a man. Just a thought.