Cas had returned in time to stop that damned knife from entering her body and reducing her to just another corpse.
He had helped her just as she had helped him before.
Meg had endured months of relentless torture to keep his and the Winchester brother's secrets, never once telling her captor what he wanted to know.
It was the least he could do, but Castiel couldn't deny there were other reasons. Selfish reasons an angel shouldn't be experiencing...
He wanted her to be alive so he could continue to enjoy her company. So he could kiss her again. So she might, perhaps, be his girlfriend.
Due to the curse laid on her, Meg couldn't change vessels as she otherwise would, and so she was forced to heal slowly as any normal human would.
He felt bad for her, of course, but he also enjoyed tending to her as she rested. It was cozy and mundane, and he loved it.
"When you recover..." He spoke as he helped her change her bandages.
Meg gave him a quizzical look.
"Would you go out on a date with me?"
Meg looked up at him, startled, and then burst out laughing. She was soon grabbing at her ribs, since laughing hurt too much in her current state.
"It wasn't a joke" He mumbled, slightly hurt.
"I know. I just can't believe you are for real... you really are my unicorn"
He smiled at her warmly, feeling a hint of hope and he clung to it tightly.
"Is that a yes?"
"Yes, Clarence. I'll go on a date with you"