You know I can't see the scenario of Sheila sleeping with June,knowing how they didn't get on. I'm sure they had seen enough of each other during the day,let alone that Sheila was dog tired that Tuesday night and probably just wanted to flop onto her bed. Maybe the twins put the slippers there as a joke? I also think Jeremy would have studied the family routine on the Sunday and Monday night and Nevill sleeping in Sheila's room would have been a complication.