Chibiusa has come because hey, party! And food. Where there was a party with food there was surely to be cake. Lots and lots of cake. She was in just a pink and sparkly gown, her hair done up. She had made sure there was enough room in the good for well... eating.
She'd wait for the buffet to be less crowded though and was too interested in looking at the giant cake and cupcake section for the main wedding cake. It was gorgeous. She walked past Mamoru, giving a happy wave before heading off for the way of the buffet maybe. Unless he said anything.