Have to admit I freaked out when the guy said she was just visiting! But having calmed down and thought about it, how could he possibly know what she was doing there? Unless he’s working on the set, but that doesn’t appear to be the case. What do you think?

I think exactly the same as you do. If he’s working on set, I doubt he’d be tweeting about what happens there, and if he’s not working on set, he has absolutely no way to know what she was there for. And even if she’s indeed visiting, nothing says she won’t be working there later. The more I think about it, the more I realize I’m actually pretty pleased with this news.