Friend tried to trick me into babysitting

This happened long ago, but even after 25 years I can't wrap my head around it. My husband and I were graduate students and we, like most of our friends, lived on a low budget. One of our classmates was engaged to a guy with a lot of money--think hot-shot stockbroker in the late 1990s. He was clearly training her in The Ways of the Entitled. They had a little boy together.

We didn't see them much because we couldn't afford most of the restaurants or events they suggested. My friend, however, acted like we were just avoiding her no matter how much we reminded her the costs were out of reach for us.

One Saturday evening, she called and started out with: "We haven't hung out in so long. How about you two come over and we'll get a pizza or something." I said we'd love to come. Then she said, "Great. And after you put \[3 yr old\] to bed, you can just watch a movie or something."

I was confused and asked why we would put her son to bed. Weren't we going to hang out? She replied, "Oh, fiancé and I are going to a party in the neighborhood. We'd invite you to come along but the hosts don't even know you and that would be awkward. But we should have time to chat before we leave."

I said I didn't want to be her free babysitter. She got annoyed and said it wasn't free because they'd get us a pizza. I said 'no thanks' and she was so shocked--"WHAT?! Now you're not coming? What are we supposed to do now?" Keep in mind it had been only about 40 seconds since I figured out she expected us to babysit.

I imagine she spent the party complaining about the friends who were supposed to watch her kid but bailed on the the last minute.