Interesting Playdate

Avery had a friend over this afternoon...for most of the afternoon they played together, in the same room. Toward the end, however, Avery was just wandering around in the living room and kitchen while her friend stayed in the girls' bedroom with Reese. Assuming Avery was mad, even though she looked totally normal, I asked what was wrong and she said "Nothing." I asked her why she wasn't playing with her friend and Reese and she said "We're pretending like we're divorced." So basically, they spent a good 10-15 minutes in separate rooms, doing separate things. And here I thought the whole concept of a playdate was for them to get to play together.
What's next? Pretending to be poor? Out of work? Frustrated with cleaning up after kids who don't appreciate it?
I will never understand the mind of a child.