Who would be considered the rude one in the following situation:?

You go to dinner with your husband. Someone you only know as an acquaintance (no one you could actually call a friend because you can’t stand being around them for more than 10 minutes at a time) shows up at the restaurant as you’re waiting in line and asks if you’d like to dine with them at their table. Well, “No, not really!” is what you’re thinking. But you can’t say that. You almost have to accept, which puts you on the spot. However, if you had said, “No, thank you,” would you have been the rude one, or was the acquaintance the rude one for presuming and putting you on the spot? (Uh, yeah. We ate with them. 40 minutes of misery.)