Who is Mina from Collected Stories and what is their importance?

Mina is the young woman in "Artificial Roses" who races off to Mass in a wet, wrinkled dress then returns shortly afterward. She disappears into the bathroom, where her blind grandmother hears he flushing something down the toilet. When she emerges, the grandmother says she knows that the girl has been staying up late at night writing love letters, and that Mina came back so soon after leaving for Mass because someone (her boyfriend) she was supposed to meet on the way to church disappointed her.