Why couldn’t Betty join the dancing party?

M: We are going to have a dancing party tonight. Would you like to join us, Betty?
W: No, I’m afraid not. I have an appointment with my history professor tonight.

W: I want to go to the concert tonight, but it starts at ? ,and I have to work until 5. There won’t be enough time to go home for dinner.
M: I’ve an idea, I’ll pick you up after work and we’ll eat downtown. That’ll give us plenty of time to get to the concert.
W: It’s a good idea.