I imagine it goes something like this : He asked a girl to a dance, then her mom contacts him to inform him she and her other child are coming along. At this point he starts to regret asking the daughter in the first place and gets totally overwhelmed. This fun dance event is now a stressful family event, and he realizes that asking this girl was a big mistake. He takes steps to stop the train before it gets more out of control. He runs from girl and overbearing family, and never looks back. Just my thoughts, but as a young college kid, asking someone on a date is scary enough. Having the family invite themselves along is too much added pressure & stress. It clearly would be more fun to invite someone else along, who just wants to go to the dance.
In my opinion, he is smart to run from this family and cut all ties. Especially since they are the type to try to ruin his future and career over a DANCE invitation. It is ridiculous.
How old is this girl, we never got the answer? I think a HUGE part of the story that is missing is the age of the girl who was to be going to the dance. That makes a difference in whether or not her mom is a crazy person or acting rational.