"I understand." He still frowned as he said this, but he did understand. While he'd been unaware of the full scope of the situation until just moments prior, he understood why she couldn't be around the Winchesters. Their relationship with her was not rooted in trust like his was. If there was someone they trusted even less than him, it was Meg. When she mentioned her death, he wished he'd been told about her death sooner. He wasn't entirely certain of the scope of time that passed after what transpired in Lucifer's crypt, but to go that long without finding out what happened to Meg was something that made him wonder if he ever would have found out, had they not come across one another in Oakdell. If he thought about it too long, it would lead him to his answer that he would have gone unaware of it for the rest of his days.
"I care about you," he told her after a moment. It was out there, point blank and had that blunt honesty that still sounded earnest that only Castiel managed to possess. "It's not simply to do with my memory of the pizza man, although that is a fond memory. A happy one. One of the few that I have." Some of his memories were tinged with blood now, with the knowledge that he either saw this brother or sister die or was the cause of their death. Or times with the Winchesters, where he had quite a few unhappy memories to counter act all the good ones that he had because of them. Free will and making his own choices, his own path had been both a blessing and a curse in that regard.