I think that when Emily goes to the bathroom because she is unwell at the party she insists that the MC go home instead of staying to wait for her because either she is already with someone in the bathroom or she is waiting for that someone. If it is not absurd that he insists so much that the MC go home alone. And I also do not understand how the MC leaves his girl drunk at a teenage party, and more with the antecedents of cheating that she already has