Warning, this is more like an AU, so most of this did not actually happen. This isn't exactly how I would make it happen either, I'm just making it up as I go.

Natasha: wanted to go with boris, but met Andrei, but he isn't here, so she's going with pierre

Sonya: Was going with Nikolai, found out he no longer has feelings for her, they broke up, and dolokhov used it as a chance to ask sonya out, and sonya says yes.

Marya: Is a chaparone

Anatole: Is there and checking out all of the girls like the creepy fool he is

Helene: Is there for the free food

Dolokhov: Is there with sonya and couldn't be happier

Bolkonksy: Is asleep and at home

Balaga: Is swinging from a light somewhere

Mary: Is home as always do everything she can not to anger her father, and to help him.

Nikolai: Is with Mary helping her.