"Figure if I start now you might believe I mean it by the time December rolls around." There's a little bit of a teasing note to the way she says it, light and playful. Just enough to make it clear that she means it, but she's not going to dwell on it. The invitation isn't conditional on anything other than genuinely wanting to make sure he has plans for the holiday.

His question about a plus one does make her chuckle a little. "I was their only babysitter for about ten years. I think they trust my judgment for holiday guests."