Sam took a deep breath, too, because there was a lot more tension in the room right now than there really needed to be. She wanted to raise her hands to run over her face or through her hair, classic gestures of frustration and discomfort, but instead she kept them folded across her belly. This was the kind of situation where she was somewhat glad for her height, not because she wanted to be intimidating, but just because straightening her spine and feeling the extra height it gave her was, in a weird way, reassuring. A physical movement that would have made her more prepared to take on a physical situation, which somehow made her feel more capable of handling the emotional and mental situation.
She had already turned back to face Meg, but she was quiet for a moment before speaking. "Alright," she said. "I'll make you a deal. I won't ask you about your background in your world, but you can't hold any of that-- or judge me based on any of it-- either. Because you don't know me. You know a version of me. It might be a close thing, but it's not the same. And if you're not going to explain yourself enough for me to figure out what's different or similar about you to someone I know, then I'm not going to explain anything, either. Clean slate, both ways."
Or at least as much as was possible. Undoubtedly, Meg would end up finding out more about her through Cas than Sam was likely to find out from Cas about Meg, but there wasn't much that could be helped there. But the offer of judging solely on what happened to them here, and not in their own worlds, was basically the stance she'd already decided to take-- it just wasn't something she'd voiced aloud until now. After all, she was already dealing with a version of the angel who'd tried to kill her and her parents, and a future version of Castiel who had made mistakes that, under other circumstances (if she'd experienced them herself, for instance) she might have held against him. But she'd let all of that go.
She would have preferred to know what it was she was letting go of for Meg, but she supposed it didn't really matter anyway. What if she was a version of Mel, or something worse? Would she really do anything differently? Probably not.
She relaxed her posture, and gestured with one hand toward the door. "If you want to go and check on your Cas, don't let me hold you up."