What is a summary of chapter 20 of Lyddie?

As chapter 20 opens, Lyddie no longer has the company of either her sister Rachel or Diana Goss. She has recovered sufficiently from her illness to be back to her old speed, and she has broadened her reading selections to the Bible and other Dickens pieces. More Irish girls are coming to work at the factory, and Lyddie becomes closer to Brigid, teaching her the ABCs and to read at the factory and in the evenings. 

One day Lyddie receives a letter that her mother has died. She doesn't react much because in a way her mother was "gone long before she died." 

Leaving the factory one evening, Lyddie expects to go out with Brigid but finds she isn't there. She re-enters the factory to hear Brigid pleading with Mr. Marsden. Lyddie realizes that Mr. Marsden is being abusive toward Brigid. She grabs a bucket of water and brings the whole bucket down on top of the overseer's head. Then she and Brigid run out. Lyddie can't stop laughing because the overseer with the bucket on his head reminds her of the bear in their cabin in chapter 1. She keeps laughing as she runs away from the factory, pulling Brigid along with her.