Ophelia and Alexei
Alexei knew he could not monopolize his cousin - his betrothed. She had specifically asked him to give her time with her friends, and so he was giving her that. Alexei knew some of her friends were guys, and she wasn't going to want him around for that. He didn't want to be around for that. He had started to go to the refreshment table to give her a chance to have some fun without him, but worried he was just going to be watching her with other guys.
Instead, he went outside the doors of the Great Hall. There were less people out here, and he could always say he was just getting some air.