Ok, here’s my guess:
Sanae is thinking of how to get more money for her shrine and Nitori suggests selling advertising space on their clothing like racecar drivers, then either she does it and Hecatia gets the wrong idea and offers Sanae one of her ugly shirts which makes Sanae cringe, offers to pay for her to wear a shirt like that and gets her to cringe, or she is bringing up looking like Hecatia as a reason not to do that entirely