She has no idea why it keeps happening. Which isn't to say she minds it, because she really doesn't. It's surprisingly easy and relaxed to talk to Charlie, and he's - yeah, he's a friend. And the idea that he likes her company is kind of nice, even if she has very little to no idea why that would be. She can be personable, sure, but she doesn't tend to make a specific effort these days. And she has no illusions about her normal self being someone who's friendly or easy to get to know.

Also she's pretty sure Tony thinks she's sleeping with Charlie, and that idea she doesn't even know what to start to do with so she just leaves it alone.

Tonight may be late, but she's up. She generally is at this hour, even if her blink of surprise at his appearance is a little slow, somewhere starting to border on sleepy. "Charlie? What are you doing still up?"