Stepping back Buffy reached for her flask in her back pocket. "Hold old you hand." she requested, before adding, "Please. I need to check something." If she did it easily that in itself was probably proof that she wasn't possessed, but she had to be sure.
Smiling slightly, Buffy looked almost tired for a moment. "I'm older." Dawn did look younger, that she did notice. "I'm from 2008, what year was in for you before you got here?" how much had changed, and what didn't she know about her future? Maybe she hadn't been a giant, and doll and...yeah, that would probably be better.
At least she had Andrew from her time. But if Dawn was from too far in the past then she might seriously have a hate for both Andrew and Spike. There was going to have to be a lot of explanations given.