How and why did Rachel's arrival change Lyddie's attidude toward Brigid in Lyddie?
Lyddie loves Rachel and immediately recognizes her little sister's helplessness and vulnerability; she is moved to do everything she can to make life better for her. Having Rachel with her to care for increases Lyddie's burden, but also expands her capacity for sympathy and compassion. When the overseer has Lyddie relay the message to Brigid that she will have to speed up or she will be fired, Lyddie is at first annoyed. Her attitude is that Brigid needs to learn "to bear her own troubles"; Lyddie does not want to be saddled with the responsibility of taking care of her.
When Lyddie delivers the overseer's message to Brigid,
"the girl's eyes (widen) in fear, reminding Lyddie, oh cuss it, of Rachel's silent face as the child sat crouched within herself in the corner of Mrs. Bedlow's kitchen".
Despite herself, she is moved to help the new girl, telling her gruffly,
"Oh, tarnation...I'll help you...we'll do the five looms together for a few days - just till you get on better, ey?"
Lyddie's recognition of Rachel's need enables to recognize that same need in others. Even though she is annoyed and frustrated at having to take responsibility for Brigid at the expense of her own work, Lyddie is moved to be kind and help her get by (Chapter 15).