To get this event to trigger, you will need to meet a couple requirements:
Need to be in stage 3
Sex Obsession > 10
Humiliation > 10
Once you meet these requirements, head to the canteen to get lunch. While in line you'll hear some laughter and see a bit of fun going on at one of the tables. Choose to go over and have some fun yourself.Â
Once you get to the table, you'll see who is the bigger slut between yourself and Erica. There are no skill checks in this so to win just always choose to act sluttier and not the "give up" options.
Winning the bimbo off against Erica will unlock two conversations. One with Candy and one with Mrs. Antlers. The candy conversation happens next time you visit her at work, the Mrs. Antlers option is an option when talking with her after work.