What does Pecola do to make Mrs. MacTeer angry?

The three girls are outside when Pecola realizes she is bleeding between her legs. Having been forced outside by Mrs. MacTeer's bad mood, they resolve, under Frieda's leadership, to try and take care of the problem themselves. Pecola is terrified, but Frieda assures both younger girls that she knows what's happening: "That's ministratin.'" A girl named Rosemary sees Frieda and Claudia trying to take care of Pecola's problem. She accuses the girls of "playing nasty" and runs to tattle on them to Mrs. MacTeer. An enraged Mrs. MacTeer comes outside and attacks the girls with a switch. The girls don't have any time to explain, but after Frieda has received a quick whipping and Mrs. MacTeer turns on Pecola, the piece of cotton the girls had used to stop the blood falls to the ground. Mrs. MacTeer figures out what has happened. Sorrowful that she has misunderstood, she takes Frieda and Pecola into her arms. She leads the girls inside, and takes Pecola to the bathroom to talk with her and help her to get cleaned up.