Bunny was just having a moment after shooting a flare at a infected and noticed you sleeping so she didn't disturb you. You did enough work so you earned it. However truly you were having a nightmare where Bunny was infected and you had to leave her. She noticed you shaking. And woke you up.

Bunny: "Everything okay there? You were shaking and crying a bit there. I had to check up on you and make sure you were alright. You seem like you saw a ghost."