While Maeve is best at flying around an open map, a closed environment doesn't hinder her performance. Use Prowl to speed around corners, and jump INTO corners to confuse the enemy.
If you happen to come across Khan, use the environment to your advantage. Get hits from a distance, run around, and get more hits on him. His relatively small shield lets you get more shots at him, too.
Khan is usually only a threat to the backline when he has his ultimate. Stay behind or inside your Frontline's shield to prolong or avoid Khan's ultimate completely as he cannot grab anyone behind a Shield.