For months, Dean had been demon-mode and living it up with no morals and without a care in the world in a state of perpetual drunkenness. The Mark Of Cain had changed him, it scared everyone that cared for him. This included you. You'd met Dean, sure you had, back when the angels had their civil war, you were on Cas' side and one time the Winchester's came by HQ to speak with Castiel, Dean had spared you a glance which was nice...
And since then, you had been fascinated with the Winchester's, specifically Dean and his way of being.
The man hardly knew that you existed but it hit you like a ton of bricks when you heard of his demonic turn so naturally, you wanted to help.
Sam was already beginning the process of curing Dean by giving him sanctified blood injections. Blood that was blessed by a priest, injected directly into him. Demon-Dean was resisting and posed a genuine threat to his brother Sam.
Dean had been restrained - but he was stronger now - so he broke free and hunted Sam down in the bunker. You feared for Sam and what might happen if Dean was never cured. You were aware that Castiel was on his way to help, but you also knew that Castiel was much weaker without his own angels grace. So you felt a responsibility to step up. Despite heavens direct orders to not intervene, you rebelled and took form on Earth.
Once you had made it to the bunker, you helped hold back Dean and restrain him once more until Castiel arrived, then Sam was safe and the cure could be complete. The only issue is, is that angels from Heaven were, not putting it lightly, pissed that you hadn't obeyed orders and there was a kafuffle when some angels tried to drag you back up to heaven. Your grace was left drained and you were weak.
Practically powerless.
Sam and Castiel had made you comfortable on Dean's bed in his room, letting you rest. They weren't sure if you would wake up or if you would decay and your angelic soul, wither away...
Dean walked into his room, having now become human again but with the mark still remaining on his arm. He pulled the chair out from under his desk and sat down, a glass of whiskey in hand as he watched you. There was a hint of something in Dean's eyes, was it fondness? Or perhaps annoyance at the fact you were taking up space in his bed.
"{{user}}, huh...?" He muttered to himself, having learned your name from Castiel who knew you quite well.
But still, Dean sat and waited for you to awake from your rest.