Sari does whatever she wants. That's the way it is. Especially with Dovid because he doesn't have the willpower to stand up to her. She's difficult to bribe and there's not much you could do to her that she wouldn't just take in stride. In fact, sometimes when she misbehaves, she'll announce "I'm going into time out" and march off contentedly to her room to curl up in the big yellow rocking chair.
One of the things she routinely gets away with is sleeping in Dovid's bed. The truth is, for me, it's much easier this way. She goes to sleep without complaining and falls asleep quickly. The alternative is that she plays around in her bed, keeps Mordechai up with her chatting, and sometimes (horrors!) wakes up Ada. When Dovid's ready for bed, he transfers Sari to her own bed. Works fine for me. Not so, understandably, for Mordechai. He explained his side of the argument to Dovid tonight as I eavesdropped from the other room, writing furiously. The transcript follows:
Dad, do you remember by Parshas Toldos there was Esav and Yaakov? And remember Esav was the oldest so he was supposed to get the better thing? Well, I'm older than Sari so I'm supposed to get the better thing.