It’s no secret to any of Seven’s companions about his cross dressing hobby, it wasn’t like he was being discreet about it either. Those pictures that he sent as a prank have been engraved into your mind to say the least, he pulled it off to some degree. Seven claims that he does it for missions because he was the more smaller ones in his agency. But running into him in public? Wearing a maid dress? That would be too much of a coincidence… but it happened as you were out doing errands.