Castiel could certainly understand her dismay at having been turned into a little yarn doll. He had been turned into an action figure years ago. It wasn't something he'd ever discussed with her (or talked about with anyone, really), or something he really planned to discuss with her, unless she needed to talk to someone.
Though, without Dean and Sam here, there was no reason to keep the woman in the dark. He'd wanted to tell her everything from the start, it had only been at Dean's insistence that he'd kept his silence (mostly).
"Lucifer has returned. He's gotten a human woman pregnant and killed Crowley. Dean told me that Lucifer killed me shortly after that.." Castiel couldn't remember, of course.. and he was glad for it. Who wanted to remember their death? "But Jack-- that's the Nephilim-- I feel he's good. I think he'll do good." And for the angel (well, archangel now, thanks to Knowhere), that feeling was all important. He'd gone from wanting to kill the woman and her baby, to wanting to protect the baby-- to raise it and teach it right from wrong. To love it. What a strange feeling.
The angel let silence hang between them a few long seconds until he finally spoke again. "I'm sorry, about what happened to you. It was entirely my fault." It hadn't been, of course.. he shared the blame with Sam. And with Charlie herself. She'd been the one who had chosen to leave after being told she needed to stay. But Cas should have been watching her, should have ensured she stay safe and sound. He'd been distracted by Rowena and Charlie had flown the coop.. if he hadn't..
Blue eyes cast down to his hands in his lap. "If I could go back and do it again.." He would handcuff her to the table or something. Make sure she stayed put. He should have known better.