So (A) and (B) would have to be in a relationship for this one (or just comfortable enough to fall asleep together)
1.)(A) wakes up from a bad nightmare, and has to go outside to calm themselves down since they didn't want to wake up (B) by accident. After a little bit though, out they come, finding (A) in the process of a small panic attack, which leads to them trying to comfort them, and convince them to go back to sleep again.
Or
2.) Similar scenario, but (B) is already up and getting ready for the day by the time (A) woke up, so they have to delay themselves for a little bit so they can calm down (A).