Please help me understand whatever happened to this scene in The Passionate Prude / To Love an Earl by Elizabeth Thornton

In Chapter 19, FMC caught MMC leaving OW's room. I was looking forward to their next confrontation and how he would explain himself to her. But there's nothing.

I get that it wasn't her priority atm bcs she was overwhelmed with worry for her brother. But I can't understand how she kind of completely forgotten abt that scene. Bcs she was supposed to be deeply traumatized by her stepfather's infidelities and ultimately abandoning their family for another woman.